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A theoretical approach to the construction of technological output indicators
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A theoretical approach to the construction of technological output indicators P.P. S A V I O T T I Department of Liberal Studies in Science, Manchester University, Manchester M13 9PL, UK
J.S. M E T C A L F E Department of Economics, Manchester University, Manchester MI39PL, UK Final version received October 1983
In this paper a framework potentially useful for the development of indicators of the output of technological innovation is described. The approach is based on a characteristics description of product technology. A product is considered a combination of three sets of characteristics, one describing the technical features of the product, one describing the services performed by the product, and one describing the methods of its producnon. These sets of characteristics are related by patterns of mapping. The potential applications of the framework to the development of indicators of the output of technological innovation and to the analysis of diffusion and technological substitution are outlined. Also, the relationship of this framework to the concepts of technological regimes, technological guide posts and dominant design is described.
!. Introduction
Whilst there is widespread agreement that technological innovation is an extremely important component of economic development the precise mechanisms by which this contribution occurs are not known. This is a serious handicap for any well-motivated technology policy. The policy maker wanting to know the relative ranking of various countries in terms of particular technologies, the contribution of R & D and of other sources of innovation to improvements in technology will, generally, have to rely on input indicators. In spite of the undoubted usefulness of input Research Policy 13 (1984) 141-151 North-Holland
indicators a proper assessment of innovation and technology policies cannot be made without output indicators. Considerable efforts have been made recently to develop output indicators. Very valuable results have been obtained by some authors [1], using patents as indicators of the output of innovative activity. However, like all currently available output indicators, patents have well known limitations. There is, therefore, a need to develop alternative indicators of the output of innovative activity in terms of measures of changes in the state qf a technology. In order to avoid a situation in which many unrelated indicators are developed for specific purposes, a conceptual framework which relates at least a large number of them is required. Such a framework cannot be purely empirical but must be related to theories of innovation and technical change. The construction of such a framework can therefore both serve to relate output indicators and to test innovation theories. This paper is an attempt to formulate such a framework and to relate it to some innovation theories being developed at present. This framework is not yet sufficiently developed to allow it to be used either to collect or manipulate data and the present paper is a first attempt to formulate it and to give it an initial structure. Needless to add we are attempting to reach more systematic ideas which are already lively topics for debate among students of innovation.
0048-7333/84/$3.00 © 1984, Elsevier Science Publishers B.V. (North-Holland)
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The starting point of this framework is a characteristics description of a given technology. A product will then be defined in terms of a set of characteristics. At any point in time this set of characteristics defines the current state of technology, each characteristic having variable levels. This is by no means new and it is, for example, the approach underlying some theories of consumer demand [2] and the more empirical hedonic price method [3]. In this paper an attempt is made to introduce explicitly three related sets of characteristics which will be called technical, process and service characteristics, and to predict some of the possible applications of this approach to the description of technological change and of its relationship to economic life. Of course, it is hoped that this approach can help to develop indicators of output of technological change.
2. A framework for the analysis of the evolution of technology In order to develop indicators of the output of technology the meaning of output should be unequivocally defined. A product, embodying a certain technology, will be simultaneously the output of a producer institution, generally a firm, and the input to a user institution. The user institution will be mainly interested in the services performed by the product and in the economic cost at which they are available. The producer institution, on the other hand, will have to supply those services by means of a combination of technical characteristics. This suggests that a product could be described as the combination of two sets of characteristics, called technical ( X i) and service (Y~)
Technical characteristics
Service characteristics
Pattern of mapping Fig. 1. Representation of a product as two sets of characteristics, technical and service, and a pattern of mapping.
characteristics respectively, and by a pattern of mapping, relating the two sets of characteristics mentioned above (fig. 1). The pattern of mapping will give the efficiency which which a set of technical characteristics can supply a certain level of services. It is worth noticing that this pattern of mapping bears a close resemblance to the concept of design. Clearly, many definitions of design can be given but to quote, for example, E. Layton, " . . . a t the outset design is an adaptation of means to some preconceived end" [4]. It is easy to associate means with technical characteristics and ends with service characteristics. Within this framework there will then be several possible dimensions of technological change: (a) change in absolute values of Xi; (b) change in the mixture or balance of X, (changes in weights); (c) change in the pattern of mapping ( X , ) ~ ( ~ ) ; (d) change in mixture or balance of ~; (e) change in absolute values of Yj. A change in each of these dimensions, the other dimensions being kept constant, will change the type and level of service characteristics Yj. This does not imply that changes (a), (b) and (c) preceded or caused changes in services performed. Changes in dimensions (b) and (d) can lead either to the appearance of new characteristics or to the disappearance of pre-existing ones (when their weights become zero). Consequently, changes in technology could take place either continuously, by means of changes in the levels of ~ and Yj ((a) and (e)), or discontinuously, when completely and radically new characteristics appear. Students of innovation have long been aware of the different significance of radical and incremental innovations and of the existence of continuous and discontinuous changes (e.g. switches in technological regimes). These concepts will be discussed in a later section. However, it is worth noting at this point that they are implicitly present in the proposed framework. Before proceeding further it might be useful to consider some examples to see to what extent the previous approach is applicable. Product characteristics for the motor car are given in table 1. Similar lists of characteristics for other products appear in the Appendix (tables 2 and 3). These lists of characteristics are not complete but they
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Table 1 Product characteristics - motor car Technical characteristics Engine
Engine
Transmission Transmission
Service characteristics
Economic environment (COSTS)
Type
Main
Speed
Size
services
No. passengers
No. cylinders Bore Stroke Compression ratio Carburettor Injection Position No. gears
Luggage space Complementary services
Ventilation Comfort Radio Instruments
Externalities
Pollution Noise Space occupied Danger to occupants Danger to other people
Syncromesh Automatic Semi-automatic Clutch Driving wheels
Braking system
Disc/drum Power braking Circuits
Suspension
Independent Shock absorbers Leaf springs Hydropneumatic No. positions
Body Electrical system
No. volumes No. doors
are simply intended to exemplify the classification framework which is proposed in this paper. It can be seen in tables 1 and 2 that a systematic classification of service characteristics into some categories have been attempted. These categories are: main services, those services that determined in the first place the introduction of the technology; complementary services, services that facilitate the performance of the primary services, and externalities, unwanted services jointly produced that must be minimised. Such a further sub-division of service characteristics into sub-categories can be justified if the relative importance of main services, complementary services and externalities change during the evolution of a technology. Such changes in balance seem to take place during the diffusion of some technologies. A similar classification can be attempted for
Purchase Maintenance Running costs Depreciation
technical characteristics. A product, considered as a system, will have sub-systems, for example, engine, transmission, electrical apparatus, steering system, etc., for a motor car. Each of these subsystems will be described by a number of characteristics. The possibility of multicollinearity arises when several characteristics describing one sub-system are correlated. This is not necessarily just a disadvantage because one can reduce the number of characteristics required to describe a given sub-system if the relationships between different characteristics are known. It is worth noticing that both a similar classification of services and an approach to establish service characteristics' relative weights is used in value engineering [5]. Furthermore, in the same technique a clear distinction is made between form and function, where function refers to the perfor-
1,14
P.P. Saviotti and J.S. Metcalfe / Technological output indicators
mance of required services and form to the internal structure of the technological artifact used to perform the function. Therefore, there are previous examples of both the use of a characteristics approach to the description of a product (or a technology) and of the distinction between form and function. In this paper we are only proposing to combine these two approaches and to make the distinction between technical and service characteristics explicit by means of a pattern of mapping. This should improve the applicability of a characteristics approach to the evaluation of technological change and to the testing of theories of innovation. Every product is produced by means of a process. However, there are some aspects of process technology which are partly independent of the characteristics of the product. The separability of product and process technology is not complete but it is a reasonable approximation in many situations. In principle a characteristics approach similar to the one used for product technology can be extended to process technology. In fig. 2 we therefore extend our framework to capture this crucial dimension of a new technology. A second mapping is introduced from the technological characteristics X, to the process technology characteristics Z,, from which one can define types of technological change just as with the service characteristics mapping. The relevant process characteristics would include the materials and the operations performed on them (shaping, mixing, assembling, etc.), the forms of energy required and its method of transmission (human labor or machine), the organisation of the process (batch versus flow) and the various skills required by the labour force and management. In combination with the supply rentals of the various inputs to the process a supply price for the new product can then be deduced. The matching of this supply price with the demand price of the users then determines the rate of utilisation of the new technology as measured by, for example, the rate of production of the new product. The economic significance of the product and process technologies will, of course, depend upon the economic environment within which they are placed. In summary, the rate of return on capital invested in exploiting a particular technological regime will depend upon the price of inputs specified by the process characteristics and upon the
Process characteristics
Technical characteristics
Service characteristics
X2
r~
Z2
Z2
-->
zr III
Ill
process technology
\,
Product technology
Economic ] / environment: processcosts | and product [ rentals
I Relative costs and rentals of competing process and product technology. Rates of utilisation. Fig. 2. The relationship between economic environment, product and process technology.
user valuations placed upon the various service characteristics of the associated product. This rate of return will be a key determinant of the growth of productive capacity and thus of the penetration of a regime into the economic environment.
3. Relationship to innovation theories Students of technological evolution have noticed that both continuous and discontinuous changes contribute to it. The appearance of a substantially new design would be an example of a discontinuous transition whilst subsequent improvements of the same design would be examples of continuous improvement. Furthermore, a dominant design has been observed to emerge at certain stages during the evolution of some technologies. The presence of common approaches to some technological problems, at least for considerably long periods of time, has been by some authors
P.P. Savwtti and J.S. Metcalfe / Technological output indicators
7",
x~2 xl3
\
Ill ~ Y21 ](12 = Y22 Yt3 = ]I23
' X21 X22
x23 Y,m = Y~,,' X2.1 Fig. 3. Pure substitution in terms of a characteristic's framework.
variously labelled as a technological regime [6], a technological guidepost [7] or a dominant design [8]. Following Nelson and Winter we can define a technological regime as consisting of a given list of technological characteristics X~, and related to this regime will be a process technology and a product technology. This regime will have a given performance potential defined in terms of the technologically defined optimum levels of each element X~ and we can define a technological trajectory as the pattern of improvement of the various X i over time. Any trajectory will have joint implications for the set of service characteristics and the set of process characteristics. If the set of X, is changed,
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we have a change of regime and thus the definition of a new technological trajectory. Examples here would be the switch from piston engine to jet propulsion of aircraft, the switch from cast iron to plastics in pipe technology, and the switch from rear-wheel drive to front-wheel drive for motor vehicles, Since the scope for improvement within any regime is always limited it follows that changes of regime are the only long-run source of continued technical advance. It is the presence of a law of diminishing returns within a given technological regime which stimulates the search for alternative technological regimes resulting in radical innovations in spite of the considerable existing commitment to an established technological regime. The discontinuous change represented by the switch between two different technological regimes or, in other words, between two different sets of technical characteristics, is usually accompanied by an improvement, but not necessarily by a discontinuous change, in service characteristics. For example, the change from propeller to jet aircraft is a discontinuous transition from the technical point of view but its influence on the services performed consisted simply of increases in transportation speed, fuel efficiency etc. To maintain a distinction between technical, service and process characteristics can, therefore, be useful to map different aspects of technical change.
Sl 1
X12 'X.
X13 T1 ~ _
Yll
X~2
Y12
X13
El3
Ell
Y,3
x12
Z
r.,
Xl~
X21 x22
( Y21 I"22
X23
V23
T2 --
Yl,k+ 1 Y22
Yl,.
~
x22 x23 r~
/ r2m
Z t x2nl
X2.1
l Y2ml
Fig. 4. New product in terms of a characteristics framework the transition from T 1 to T2 is a change of technological regime,
Fig. 5. Partial substitution in terms of a characteristic's frame. work.
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P.P. Saviotti and J.S. Metcalfe / Technological output indicators
The previous distinction can also be useful to distinguish between technological substitution and the appearance of a new product. If we assume that two technologies T1 and T2 can be described by the same set of service characteristics ~ but by different sets of technical characteristics, then the replacement of T1 and T2 is both an example of pure technological substitution and of technological regime change. Such a substitution would only take place if the combination of product and process technology lowered the cost of the constant package of services provided. If, on the other hand, at a given time a new technology appears which supplies an entirely new set of services this will give rise to a new product. Of course there can be intermediate cases. For example, a new technology T2 can supply some of the services which were supplied by a pre-existing technology T~ and some services previously unavailable. This would not be a case of pure substitution but a mixture of technological substitution and appearance of a new product. The different possibilities are graphically illustrated in figs. 3, 4 and 5. Summarising, changes in technology could occur in the form of regime substitution, process innovation or product innovation.
weights of the service characteristics. The technical characteristics will be related through a pattern of mapping to the service characteristics. The weights of the technical characteristics will then depend on the weights of the service characteristics through their pattern of mapping, which measures the efficiency with which each technical characteristic contributes to each service characteristic. Let us, for example, combine all the service characteristics into an indicator of overall performance, R, by means of the selection environment weights Aj:
R --.40 + EAj
.
J
Let us consider the case in which to a first approximation the Yj are related to the X,, by a linear mapping, then: Y1 = C n X1 + C12 X2 + ... + C1~X,, 72 = c 2 , x , + c = x 2 + Ym = C m l X l + C m 2 X 2 + . . . + C m n X n ,
then, R will also be related to X~ in the following way: R = Bo + & X, + B2 X2 + ... + W. r'.
where: 4. Indicators of the state of technology
B 0 = A 0,
B 1 = A 1 C H +A2C21 + ... + A m C m l ,
What indicators of the state of technology could be constructed based on the previous framework? To start with, changes can take place in service characteristics, in technical characteristics and in the pattern of mapping between the two. These changes can also take place in the absolute level of each characteristic a n d / o r in their relative weights. All these changes must be combined into some indicators of the output of technology. In general it can be assumed that the knowledge of the technical and service characteristics will be available but their relative importance will not be known. Furthermore, the various dimensions of cost might be available in some cases but it is unlikely that they are always available. A first problem then consists of finding the weights or relative importance of service characteristics. This implies an analysis of the patterns of use of a particular technology. A market survey would give both these patterns of use and their relative importance, which could be taken as
B , = A1C1, + A2C2~ + ... + A,,C,,~.
The relative weights of the technical characteristics, or the technology actually used, will then depend on both supply (the technical coefficients C~s) and demand (the selection environment weights Aj) forces. This conclusion can be related to the debate need pull/technology push, and seems to coincide with that reached by Mowery and Rosenberg [9] after having surveyed a large number of innovation studies, The weights of the service characteristics will not always be available, so some way of approximating these weights must be found. A number of approaches can be found. For example, the sales of a particular product might be related to its service characteristics. It would then, in principle, be possible to relate sales to characteristics' levels and find their weights. On the other hand, characteristics' levels will also be related to price, and characteristics' weights could be found also through
P.P. Saviotti and J.S. Metcalfe / Technological output indicators
the relative weights of the service characteristics based on their pattern of use. In particular, the approach trying to derive relative weights from the relationship between price and technical characteristics is an application of the hedonic price method and has already been used in a number of cases [3,101. However, the availability of market survey data or of prices cannot be taken for granted. Technical data are usually easier to obtain and it might be advisable to have an indicator of technical change based on technical data only. Of course, the principle of deriving technical characteristics' relative weights from their relative contribution to the pattern of use of the technology will not be applicable. However, one could argue that the characteristics that are related to the most demanded services will vary more during a given period of time than the characteristics that are related to less demanded services. Therefore, weights that were related to the rates of change in various characteristics could be constructured. A similar method has been used by Sahal [11]. If two different states of a technology are represented by the two vectors having as components the characteristics' levels in the initial and final state then the "distance" between the two vectors will be related to the change in technology that has taken place. The distance vector will have larger components along the dimensions corresponding to the characteristics which have undergone the largest change. The components of the distance vector could then be used as characteristics' weights. Several types of distances can be defined. Sahal uses as weights the components of a vector A related to the generalised Mahalanobis distance. If A~, A 2, characteristics X 1, X 2 , . . . , X , then Sahal uses a measure of technology defined as:
Y = A I X I + A 2 X 2 . . . + A,,X,,. To summarise, then, there are two distinct approaches to the derivation of characteristics' weights: one based on their relative contribution to the pattern of use of a technology and one based on the relative changes in the various dimensions of the technology itself. Within each of these two approaches different indicators can be constructed. Clearly, none of these indicators will be perfect and in the cases in which data are available it would be advisable to calculate different indicators for purposes of comparison.
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On the process technology side, we have available the well established methods of factor productivity measurement. The process characteristics can be represented in terms of the various inputs required to produce a unit of output, with the rental prices of these inputs taken as appropriate weights. The change in productivity between two dates (0,1) can then be measured, for example, by the ratio
£,w,,°z °
1,
where the Zi is the measure of input i per unit of output. More sophisticated indices can, of course, be defined but in practical terms this arithmetic mean is of interest because of its relatively limited information requirements.
5. Other applications of the framework The representation of a technology by means of three sets of characteristics and a mapping pattern can lead to other applications in addition to the calculation of some indicators of technological change. For example, it is conceivable that it could help to differentiate radical from incremental innovations. It is implicit in the concept of a radical innovation that it represents a very considerable change with respect to past technological practice. O n the other hand and incremental innovation should differ' only with respect to the quantitative level of the technical characteristics, but it should be qualitatively similar to past technological innovations. This suggests that if some measure of distance could be calculated for different products then this distance should be far smaller for incrementally-related innovations than for different radical innovations. Therefore, if innovations were grouped on the basis of their distance, incrementally-related innovations would fall into the same cluster whilst two different radical innovations would belong to two different clusters. Furthermore, if the clustering procedure was repeated at different times the distance between different clusters could vary and in some cases previously separated clusters might partially overlap. This could provide some measure of technological convergence. The combination of this twin characteristics
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framework and of cluster analysis could, therefore, be of some help in the construction of a more accurate innovation taxonomy. Some difficulties can be expected with this approach. For example, several types of distance can be calculated and each type of distance will produce a different clustering. This approach will not, therefore, be usable as a black box providing the right answer with the required data input.
6. Some wider considerations One of the merits of the framework we have presented is that it allows one to think more clearly about two central, related issues in the study of technological change - the rate of acceptance of a technology and its interaction with the pattern of evolution of that technology. The emergence of new industries via the establishment of new technological regimes is without question the mainspring of modern economic growth. As Schumpeter observed many years ago, innovation is the fundamental element in economic development, that process of "spontaneous and discontinuous change.., which forever alters and displaces the equilibrium state previously existing" [12]. The contribution to development which a new technology makes depends upon the rate of its substitution for pre-existing methods, its rate of diffusion as this is often called. Given the set of process and service characteristics and the economic environment in which the new technology is being diffused, we expect that diffusion will follow a sigmoid path towards an upper, equilibrium asymptote - of which a logistic path would be one representative outcome. However, it will be clear that neither technology nor the economic aspects of the diffusion environment will be constant over time. A major element in our understanding of diffusion and economic advance will be the trajectory followed by the new technology. Different trajectories will be associated with different patterns of diffusion and thus different economic impacts of the new technology. We pose as a central research question, the simultaneous dynamics of trajectory improvement and the process of technology diffusion. The manner in which the diffusion interacts with the evolution of characteristics may be outlined in the following general terms. At the time of
original innovation we have a specific set of service and process characteristics which in conjunction with the economic environment determine an economic niche for the associated product. Approach to this niche will not, of course, be immediate, it will take time for potential users to learn of the advantages of the new technology, and for human and physical productive capacity to be built up. The precise path of approach to the economic niche will be reflected in various bottlenecks to the production and use of the product, with the incidence of specific bottlenecks varying as diffusion proceeds. Bottlenecks reflected in the changing relative price of production inputs a n d / o r changing consumer valuations of the service characteristics will provide economic incentives to produce the necessary changes in the process and service characteristics. The precise pattern of evolution (the trajectory) will depend upon a number of factors, in particular the economic return from a change in product or service characteristics, the nature of the mapping into the technological characteristics and the economic costs of the particular purposive research activity which generates the changes in the characteristics [13]. The pattern of technical change is partially a function of the pattern of diffusion, while the pattern of diffusion is itself influenced by induced changes in technology. In addition to the purposive research activity, we must also recognise accumulated experience as an important element in technology evolution, resuiting directly in advances of knowledge and indirectly shaping the direction of search. On the process side economists have for a long time recognised learning by doing as an important factor and it is equally important to recognise learning by using as an influence on the evolution of service characteristics, as Rosenberg has recently stressed [14]. In each case, the accumulation of experience is a function of the pace of diffusion so as to reinforce the simultaneous interaction between the diffusion process and the evolution of a technology. To some degree the pattern of trajectory improvement will reflect internal pressures within the process of knowledge acquisition, as technology builds upon technology. However, to the extent that technological advance requires the explicit commitment of resources to research, design and development, and will follow as the indirect result of learning phenomenon, then two factors will
P.P. Saviotti and J.S. Metcalfe / Technologicaloutput indicators
shape the evolution of any given trajectory: the rising marginal cost of incremental advance as the limit to the trajectory is approached; and the falling marginal benefit from investments in new knowledge as the technology is absorbed into its long-period niche (or habitat). To the not inconsiderable extent that technical change is induced by the invisible hand it will follow that the evolution of a trajectory will be shaped by the diffusion environment. Different diffusion environments (Japan, USA, Western Europe) will produce different patterns of technical advance, differences within the same regime and differences in regime. Diffusion and induced trajectory evolution should be treated as a simultaneous phenomenon, and we contemplate that the framework sketched above will facilitate this difficult task.
7. Conclusions
The characteristics framework presented in this paper can help to make progress towards the difficult problem of measuring the output of technology. The evaluation of both the effectiveness of industrial and technology policies and of the contribution of technological change to economic development depend on the solution of this problem. Thus, for example, the effectiveness of R&D policies does in the end depend on the quality and quantity of the technical change that they bring about. No claim is made to have solved the problem of measuring the output of technology. On the contrary in this paper it is assumed that no perfect indicator of technological output is either available at the moment or is likely to be developed. A plurality of indicators of technological output will be required and in this paper it is hoped to provide
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a framework that could accommodate more than one type of indicator. The characteristics framework adopted in this paper should be useful both for the collection and for the elaboration of data about the evolution of technologies.
References [1] OECD DSTI Secretariat, Patents, Invention and Innovation: A review of the papers presented at the June 1982 Workshop on patent and innovation statistics, DSTI/SPR/82/74 (OECD, Paris, 1982). [2] K.J. Lancaster, A New Approach to Consumer Theory, Journal of Political Economy 14 (1966) 133-156. [3] Z. Griliehes (Ed.), Price lndexes and Quality Change (Harvard University Press, Cambridge, 1971). [4] E. Layton, Technology as Knowledge, Technology and Culture 15 (1972) 31-41. [5] ASTME (American Society of Tool and Manufacturing Engineers), Value Engineering in Manufacturing (Prentice Hall, Englewood Cliffs, 1967). [6] R.R. Nelson and S.G. Winter, In Search of Useful Theory of Innovation, Research Policy 6 (1977) 36-76. [7] D, Sahal, Alternative Conceptions of Technology, Research Policy 10 (1981) 2-24. [8] W.J. Abernathy and J.M. Utterback, Patterns of Industrial Innovation, Technology Review 80 (1978) 41-47. [9] D. Mowery and N. Rosenberg, The Influence of Market Demand upon Innovation: a critical review of some recent empirical studies, Research Policy 8 (1979) 103-53. [10] P.P. Saviotti, P.C. Stubbs, R.W. Coombs and M. Gibbons, An Approach to the Construction of Indexes of Technological Sophistication, TechnologicalForecasting and Social Change 21 (1982) 133-147. [11] D. Sahal, A Theory of Measurement of Technological Change, International Journal of Systems Science 8 (1977) 671-682. [12] J. Schumpeter, The Theory of Economic Development (Harvard University Press, Cambridge, Mass., 1934). [13] H. Binswanger, A microeconomic Approach to Induced Innovation, Economic Journal 84 (1974) 940-58. [14] N. Rosenberg, Inside the Black Box (Cambridge University Press, Cambridge, 1982).
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Appendix Table 2 Product characteristics - agricultural tractor Technical characteristics Engine
Service characteristics Type (diesel, petrol) Size No. cylinders Bore Stroke Compression ratio Turbo compressor
Transmission
No, driving wheels No, forward gears Syncromesh Change on the move
Steering
Power steering
PTO
PTO presence No. PTO speeds PTO ( L / l )
Hydraulics
(L/I)
Main services
Economic environment (costs) Drawbar power Speed Fuel consumption
Complementary services External ities
Reliability Driver comfort
Safety Noise
Purchase price Depreciation Maintenance Running costs
P.P. Saviotti and J, S. Metcalfe / Technological output indicators Table 3 Product characteristics - plastic (PVC) pipes Technical characteristics Material
Service characteristics
Economic environment (costs)
Physical properties Specific gravity Natural coiour Clarity Colour possibili ties Odour Taste
Mechanical properties Tensile strength Elongation Bending strength Modulus of elasticity Compression strength Hardness (ball indentation)
Thermal properties Resistance to continuous heat Softening range Range of fusion • Temperature of thermal decomposition Flammability Brittle temperature Specific heat Thermal conductivity Thermal expansion
Electrical properties Volumetric resistivity Surface resistivity Dielectric constant Power factor Resistivity breakdown voltage
Physical/chemical properties Effect of aging Effect of light Weather resistance Resistance to boiling water Water absorption (24 h) Water vapour permeability Effects of acids: weak strong Effect of alkalies: weak strong Effect of organic solvents: Soluble in Swells in Resists Pipe
Outside diameter Inside diameter Colour Length Tolerance
Flow rate Max. pressure Burst rate Weight Corrosion resistance Average lifetime
Purchase Transportation Installation Maintenance
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A theoretical approach to the construction of technological output indicators P.P. S A V I O T T I Department of Liberal Studies in Science, Manchester University, Manchester M13 9PL, UK
J.S. M E T C A L F E Department of Economics, Manchester University, Manchester MI39PL, UK Final version received October 1983
In this paper a framework potentially useful for the development of indicators of the output of technological innovation is described. The approach is based on a characteristics description of product technology. A product is considered a combination of three sets of characteristics, one describing the technical features of the product, one describing the services performed by the product, and one describing the methods of its producnon. These sets of characteristics are related by patterns of mapping. The potential applications of the framework to the development of indicators of the output of technological innovation and to the analysis of diffusion and technological substitution are outlined. Also, the relationship of this framework to the concepts of technological regimes, technological guide posts and dominant design is described.
!. Introduction
Whilst there is widespread agreement that technological innovation is an extremely important component of economic development the precise mechanisms by which this contribution occurs are not known. This is a serious handicap for any well-motivated technology policy. The policy maker wanting to know the relative ranking of various countries in terms of particular technologies, the contribution of R & D and of other sources of innovation to improvements in technology will, generally, have to rely on input indicators. In spite of the undoubted usefulness of input Research Policy 13 (1984) 141-151 North-Holland
indicators a proper assessment of innovation and technology policies cannot be made without output indicators. Considerable efforts have been made recently to develop output indicators. Very valuable results have been obtained by some authors [1], using patents as indicators of the output of innovative activity. However, like all currently available output indicators, patents have well known limitations. There is, therefore, a need to develop alternative indicators of the output of innovative activity in terms of measures of changes in the state qf a technology. In order to avoid a situation in which many unrelated indicators are developed for specific purposes, a conceptual framework which relates at least a large number of them is required. Such a framework cannot be purely empirical but must be related to theories of innovation and technical change. The construction of such a framework can therefore both serve to relate output indicators and to test innovation theories. This paper is an attempt to formulate such a framework and to relate it to some innovation theories being developed at present. This framework is not yet sufficiently developed to allow it to be used either to collect or manipulate data and the present paper is a first attempt to formulate it and to give it an initial structure. Needless to add we are attempting to reach more systematic ideas which are already lively topics for debate among students of innovation.
0048-7333/84/$3.00 © 1984, Elsevier Science Publishers B.V. (North-Holland)
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The starting point of this framework is a characteristics description of a given technology. A product will then be defined in terms of a set of characteristics. At any point in time this set of characteristics defines the current state of technology, each characteristic having variable levels. This is by no means new and it is, for example, the approach underlying some theories of consumer demand [2] and the more empirical hedonic price method [3]. In this paper an attempt is made to introduce explicitly three related sets of characteristics which will be called technical, process and service characteristics, and to predict some of the possible applications of this approach to the description of technological change and of its relationship to economic life. Of course, it is hoped that this approach can help to develop indicators of output of technological change.
2. A framework for the analysis of the evolution of technology In order to develop indicators of the output of technology the meaning of output should be unequivocally defined. A product, embodying a certain technology, will be simultaneously the output of a producer institution, generally a firm, and the input to a user institution. The user institution will be mainly interested in the services performed by the product and in the economic cost at which they are available. The producer institution, on the other hand, will have to supply those services by means of a combination of technical characteristics. This suggests that a product could be described as the combination of two sets of characteristics, called technical ( X i) and service (Y~)
Technical characteristics
Service characteristics
Pattern of mapping Fig. 1. Representation of a product as two sets of characteristics, technical and service, and a pattern of mapping.
characteristics respectively, and by a pattern of mapping, relating the two sets of characteristics mentioned above (fig. 1). The pattern of mapping will give the efficiency which which a set of technical characteristics can supply a certain level of services. It is worth noticing that this pattern of mapping bears a close resemblance to the concept of design. Clearly, many definitions of design can be given but to quote, for example, E. Layton, " . . . a t the outset design is an adaptation of means to some preconceived end" [4]. It is easy to associate means with technical characteristics and ends with service characteristics. Within this framework there will then be several possible dimensions of technological change: (a) change in absolute values of Xi; (b) change in the mixture or balance of X, (changes in weights); (c) change in the pattern of mapping ( X , ) ~ ( ~ ) ; (d) change in mixture or balance of ~; (e) change in absolute values of Yj. A change in each of these dimensions, the other dimensions being kept constant, will change the type and level of service characteristics Yj. This does not imply that changes (a), (b) and (c) preceded or caused changes in services performed. Changes in dimensions (b) and (d) can lead either to the appearance of new characteristics or to the disappearance of pre-existing ones (when their weights become zero). Consequently, changes in technology could take place either continuously, by means of changes in the levels of ~ and Yj ((a) and (e)), or discontinuously, when completely and radically new characteristics appear. Students of innovation have long been aware of the different significance of radical and incremental innovations and of the existence of continuous and discontinuous changes (e.g. switches in technological regimes). These concepts will be discussed in a later section. However, it is worth noting at this point that they are implicitly present in the proposed framework. Before proceeding further it might be useful to consider some examples to see to what extent the previous approach is applicable. Product characteristics for the motor car are given in table 1. Similar lists of characteristics for other products appear in the Appendix (tables 2 and 3). These lists of characteristics are not complete but they
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Table 1 Product characteristics - motor car Technical characteristics Engine
Engine
Transmission Transmission
Service characteristics
Economic environment (COSTS)
Type
Main
Speed
Size
services
No. passengers
No. cylinders Bore Stroke Compression ratio Carburettor Injection Position No. gears
Luggage space Complementary services
Ventilation Comfort Radio Instruments
Externalities
Pollution Noise Space occupied Danger to occupants Danger to other people
Syncromesh Automatic Semi-automatic Clutch Driving wheels
Braking system
Disc/drum Power braking Circuits
Suspension
Independent Shock absorbers Leaf springs Hydropneumatic No. positions
Body Electrical system
No. volumes No. doors
are simply intended to exemplify the classification framework which is proposed in this paper. It can be seen in tables 1 and 2 that a systematic classification of service characteristics into some categories have been attempted. These categories are: main services, those services that determined in the first place the introduction of the technology; complementary services, services that facilitate the performance of the primary services, and externalities, unwanted services jointly produced that must be minimised. Such a further sub-division of service characteristics into sub-categories can be justified if the relative importance of main services, complementary services and externalities change during the evolution of a technology. Such changes in balance seem to take place during the diffusion of some technologies. A similar classification can be attempted for
Purchase Maintenance Running costs Depreciation
technical characteristics. A product, considered as a system, will have sub-systems, for example, engine, transmission, electrical apparatus, steering system, etc., for a motor car. Each of these subsystems will be described by a number of characteristics. The possibility of multicollinearity arises when several characteristics describing one sub-system are correlated. This is not necessarily just a disadvantage because one can reduce the number of characteristics required to describe a given sub-system if the relationships between different characteristics are known. It is worth noticing that both a similar classification of services and an approach to establish service characteristics' relative weights is used in value engineering [5]. Furthermore, in the same technique a clear distinction is made between form and function, where function refers to the perfor-
1,14
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mance of required services and form to the internal structure of the technological artifact used to perform the function. Therefore, there are previous examples of both the use of a characteristics approach to the description of a product (or a technology) and of the distinction between form and function. In this paper we are only proposing to combine these two approaches and to make the distinction between technical and service characteristics explicit by means of a pattern of mapping. This should improve the applicability of a characteristics approach to the evaluation of technological change and to the testing of theories of innovation. Every product is produced by means of a process. However, there are some aspects of process technology which are partly independent of the characteristics of the product. The separability of product and process technology is not complete but it is a reasonable approximation in many situations. In principle a characteristics approach similar to the one used for product technology can be extended to process technology. In fig. 2 we therefore extend our framework to capture this crucial dimension of a new technology. A second mapping is introduced from the technological characteristics X, to the process technology characteristics Z,, from which one can define types of technological change just as with the service characteristics mapping. The relevant process characteristics would include the materials and the operations performed on them (shaping, mixing, assembling, etc.), the forms of energy required and its method of transmission (human labor or machine), the organisation of the process (batch versus flow) and the various skills required by the labour force and management. In combination with the supply rentals of the various inputs to the process a supply price for the new product can then be deduced. The matching of this supply price with the demand price of the users then determines the rate of utilisation of the new technology as measured by, for example, the rate of production of the new product. The economic significance of the product and process technologies will, of course, depend upon the economic environment within which they are placed. In summary, the rate of return on capital invested in exploiting a particular technological regime will depend upon the price of inputs specified by the process characteristics and upon the
Process characteristics
Technical characteristics
Service characteristics
X2
r~
Z2
Z2
-->
zr III
Ill
process technology
\,
Product technology
Economic ] / environment: processcosts | and product [ rentals
I Relative costs and rentals of competing process and product technology. Rates of utilisation. Fig. 2. The relationship between economic environment, product and process technology.
user valuations placed upon the various service characteristics of the associated product. This rate of return will be a key determinant of the growth of productive capacity and thus of the penetration of a regime into the economic environment.
3. Relationship to innovation theories Students of technological evolution have noticed that both continuous and discontinuous changes contribute to it. The appearance of a substantially new design would be an example of a discontinuous transition whilst subsequent improvements of the same design would be examples of continuous improvement. Furthermore, a dominant design has been observed to emerge at certain stages during the evolution of some technologies. The presence of common approaches to some technological problems, at least for considerably long periods of time, has been by some authors
P.P. Savwtti and J.S. Metcalfe / Technological output indicators
7",
x~2 xl3
\
Ill ~ Y21 ](12 = Y22 Yt3 = ]I23
' X21 X22
x23 Y,m = Y~,,' X2.1 Fig. 3. Pure substitution in terms of a characteristic's framework.
variously labelled as a technological regime [6], a technological guidepost [7] or a dominant design [8]. Following Nelson and Winter we can define a technological regime as consisting of a given list of technological characteristics X~, and related to this regime will be a process technology and a product technology. This regime will have a given performance potential defined in terms of the technologically defined optimum levels of each element X~ and we can define a technological trajectory as the pattern of improvement of the various X i over time. Any trajectory will have joint implications for the set of service characteristics and the set of process characteristics. If the set of X, is changed,
145
we have a change of regime and thus the definition of a new technological trajectory. Examples here would be the switch from piston engine to jet propulsion of aircraft, the switch from cast iron to plastics in pipe technology, and the switch from rear-wheel drive to front-wheel drive for motor vehicles, Since the scope for improvement within any regime is always limited it follows that changes of regime are the only long-run source of continued technical advance. It is the presence of a law of diminishing returns within a given technological regime which stimulates the search for alternative technological regimes resulting in radical innovations in spite of the considerable existing commitment to an established technological regime. The discontinuous change represented by the switch between two different technological regimes or, in other words, between two different sets of technical characteristics, is usually accompanied by an improvement, but not necessarily by a discontinuous change, in service characteristics. For example, the change from propeller to jet aircraft is a discontinuous transition from the technical point of view but its influence on the services performed consisted simply of increases in transportation speed, fuel efficiency etc. To maintain a distinction between technical, service and process characteristics can, therefore, be useful to map different aspects of technical change.
Sl 1
X12 'X.
X13 T1 ~ _
Yll
X~2
Y12
X13
El3
Ell
Y,3
x12
Z
r.,
Xl~
X21 x22
( Y21 I"22
X23
V23
T2 --
Yl,k+ 1 Y22
Yl,.
~
x22 x23 r~
/ r2m
Z t x2nl
X2.1
l Y2ml
Fig. 4. New product in terms of a characteristics framework the transition from T 1 to T2 is a change of technological regime,
Fig. 5. Partial substitution in terms of a characteristic's frame. work.
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The previous distinction can also be useful to distinguish between technological substitution and the appearance of a new product. If we assume that two technologies T1 and T2 can be described by the same set of service characteristics ~ but by different sets of technical characteristics, then the replacement of T1 and T2 is both an example of pure technological substitution and of technological regime change. Such a substitution would only take place if the combination of product and process technology lowered the cost of the constant package of services provided. If, on the other hand, at a given time a new technology appears which supplies an entirely new set of services this will give rise to a new product. Of course there can be intermediate cases. For example, a new technology T2 can supply some of the services which were supplied by a pre-existing technology T~ and some services previously unavailable. This would not be a case of pure substitution but a mixture of technological substitution and appearance of a new product. The different possibilities are graphically illustrated in figs. 3, 4 and 5. Summarising, changes in technology could occur in the form of regime substitution, process innovation or product innovation.
weights of the service characteristics. The technical characteristics will be related through a pattern of mapping to the service characteristics. The weights of the technical characteristics will then depend on the weights of the service characteristics through their pattern of mapping, which measures the efficiency with which each technical characteristic contributes to each service characteristic. Let us, for example, combine all the service characteristics into an indicator of overall performance, R, by means of the selection environment weights Aj:
R --.40 + EAj
.
J
Let us consider the case in which to a first approximation the Yj are related to the X,, by a linear mapping, then: Y1 = C n X1 + C12 X2 + ... + C1~X,, 72 = c 2 , x , + c = x 2 + Ym = C m l X l + C m 2 X 2 + . . . + C m n X n ,
then, R will also be related to X~ in the following way: R = Bo + & X, + B2 X2 + ... + W. r'.
where: 4. Indicators of the state of technology
B 0 = A 0,
B 1 = A 1 C H +A2C21 + ... + A m C m l ,
What indicators of the state of technology could be constructed based on the previous framework? To start with, changes can take place in service characteristics, in technical characteristics and in the pattern of mapping between the two. These changes can also take place in the absolute level of each characteristic a n d / o r in their relative weights. All these changes must be combined into some indicators of the output of technology. In general it can be assumed that the knowledge of the technical and service characteristics will be available but their relative importance will not be known. Furthermore, the various dimensions of cost might be available in some cases but it is unlikely that they are always available. A first problem then consists of finding the weights or relative importance of service characteristics. This implies an analysis of the patterns of use of a particular technology. A market survey would give both these patterns of use and their relative importance, which could be taken as
B , = A1C1, + A2C2~ + ... + A,,C,,~.
The relative weights of the technical characteristics, or the technology actually used, will then depend on both supply (the technical coefficients C~s) and demand (the selection environment weights Aj) forces. This conclusion can be related to the debate need pull/technology push, and seems to coincide with that reached by Mowery and Rosenberg [9] after having surveyed a large number of innovation studies, The weights of the service characteristics will not always be available, so some way of approximating these weights must be found. A number of approaches can be found. For example, the sales of a particular product might be related to its service characteristics. It would then, in principle, be possible to relate sales to characteristics' levels and find their weights. On the other hand, characteristics' levels will also be related to price, and characteristics' weights could be found also through
P.P. Saviotti and J.S. Metcalfe / Technological output indicators
the relative weights of the service characteristics based on their pattern of use. In particular, the approach trying to derive relative weights from the relationship between price and technical characteristics is an application of the hedonic price method and has already been used in a number of cases [3,101. However, the availability of market survey data or of prices cannot be taken for granted. Technical data are usually easier to obtain and it might be advisable to have an indicator of technical change based on technical data only. Of course, the principle of deriving technical characteristics' relative weights from their relative contribution to the pattern of use of the technology will not be applicable. However, one could argue that the characteristics that are related to the most demanded services will vary more during a given period of time than the characteristics that are related to less demanded services. Therefore, weights that were related to the rates of change in various characteristics could be constructured. A similar method has been used by Sahal [11]. If two different states of a technology are represented by the two vectors having as components the characteristics' levels in the initial and final state then the "distance" between the two vectors will be related to the change in technology that has taken place. The distance vector will have larger components along the dimensions corresponding to the characteristics which have undergone the largest change. The components of the distance vector could then be used as characteristics' weights. Several types of distances can be defined. Sahal uses as weights the components of a vector A related to the generalised Mahalanobis distance. If A~, A 2, characteristics X 1, X 2 , . . . , X , then Sahal uses a measure of technology defined as:
Y = A I X I + A 2 X 2 . . . + A,,X,,. To summarise, then, there are two distinct approaches to the derivation of characteristics' weights: one based on their relative contribution to the pattern of use of a technology and one based on the relative changes in the various dimensions of the technology itself. Within each of these two approaches different indicators can be constructed. Clearly, none of these indicators will be perfect and in the cases in which data are available it would be advisable to calculate different indicators for purposes of comparison.
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On the process technology side, we have available the well established methods of factor productivity measurement. The process characteristics can be represented in terms of the various inputs required to produce a unit of output, with the rental prices of these inputs taken as appropriate weights. The change in productivity between two dates (0,1) can then be measured, for example, by the ratio
£,w,,°z °
1,
where the Zi is the measure of input i per unit of output. More sophisticated indices can, of course, be defined but in practical terms this arithmetic mean is of interest because of its relatively limited information requirements.
5. Other applications of the framework The representation of a technology by means of three sets of characteristics and a mapping pattern can lead to other applications in addition to the calculation of some indicators of technological change. For example, it is conceivable that it could help to differentiate radical from incremental innovations. It is implicit in the concept of a radical innovation that it represents a very considerable change with respect to past technological practice. O n the other hand and incremental innovation should differ' only with respect to the quantitative level of the technical characteristics, but it should be qualitatively similar to past technological innovations. This suggests that if some measure of distance could be calculated for different products then this distance should be far smaller for incrementally-related innovations than for different radical innovations. Therefore, if innovations were grouped on the basis of their distance, incrementally-related innovations would fall into the same cluster whilst two different radical innovations would belong to two different clusters. Furthermore, if the clustering procedure was repeated at different times the distance between different clusters could vary and in some cases previously separated clusters might partially overlap. This could provide some measure of technological convergence. The combination of this twin characteristics
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framework and of cluster analysis could, therefore, be of some help in the construction of a more accurate innovation taxonomy. Some difficulties can be expected with this approach. For example, several types of distance can be calculated and each type of distance will produce a different clustering. This approach will not, therefore, be usable as a black box providing the right answer with the required data input.
6. Some wider considerations One of the merits of the framework we have presented is that it allows one to think more clearly about two central, related issues in the study of technological change - the rate of acceptance of a technology and its interaction with the pattern of evolution of that technology. The emergence of new industries via the establishment of new technological regimes is without question the mainspring of modern economic growth. As Schumpeter observed many years ago, innovation is the fundamental element in economic development, that process of "spontaneous and discontinuous change.., which forever alters and displaces the equilibrium state previously existing" [12]. The contribution to development which a new technology makes depends upon the rate of its substitution for pre-existing methods, its rate of diffusion as this is often called. Given the set of process and service characteristics and the economic environment in which the new technology is being diffused, we expect that diffusion will follow a sigmoid path towards an upper, equilibrium asymptote - of which a logistic path would be one representative outcome. However, it will be clear that neither technology nor the economic aspects of the diffusion environment will be constant over time. A major element in our understanding of diffusion and economic advance will be the trajectory followed by the new technology. Different trajectories will be associated with different patterns of diffusion and thus different economic impacts of the new technology. We pose as a central research question, the simultaneous dynamics of trajectory improvement and the process of technology diffusion. The manner in which the diffusion interacts with the evolution of characteristics may be outlined in the following general terms. At the time of
original innovation we have a specific set of service and process characteristics which in conjunction with the economic environment determine an economic niche for the associated product. Approach to this niche will not, of course, be immediate, it will take time for potential users to learn of the advantages of the new technology, and for human and physical productive capacity to be built up. The precise path of approach to the economic niche will be reflected in various bottlenecks to the production and use of the product, with the incidence of specific bottlenecks varying as diffusion proceeds. Bottlenecks reflected in the changing relative price of production inputs a n d / o r changing consumer valuations of the service characteristics will provide economic incentives to produce the necessary changes in the process and service characteristics. The precise pattern of evolution (the trajectory) will depend upon a number of factors, in particular the economic return from a change in product or service characteristics, the nature of the mapping into the technological characteristics and the economic costs of the particular purposive research activity which generates the changes in the characteristics [13]. The pattern of technical change is partially a function of the pattern of diffusion, while the pattern of diffusion is itself influenced by induced changes in technology. In addition to the purposive research activity, we must also recognise accumulated experience as an important element in technology evolution, resuiting directly in advances of knowledge and indirectly shaping the direction of search. On the process side economists have for a long time recognised learning by doing as an important factor and it is equally important to recognise learning by using as an influence on the evolution of service characteristics, as Rosenberg has recently stressed [14]. In each case, the accumulation of experience is a function of the pace of diffusion so as to reinforce the simultaneous interaction between the diffusion process and the evolution of a technology. To some degree the pattern of trajectory improvement will reflect internal pressures within the process of knowledge acquisition, as technology builds upon technology. However, to the extent that technological advance requires the explicit commitment of resources to research, design and development, and will follow as the indirect result of learning phenomenon, then two factors will
P.P. Saviotti and J.S. Metcalfe / Technologicaloutput indicators
shape the evolution of any given trajectory: the rising marginal cost of incremental advance as the limit to the trajectory is approached; and the falling marginal benefit from investments in new knowledge as the technology is absorbed into its long-period niche (or habitat). To the not inconsiderable extent that technical change is induced by the invisible hand it will follow that the evolution of a trajectory will be shaped by the diffusion environment. Different diffusion environments (Japan, USA, Western Europe) will produce different patterns of technical advance, differences within the same regime and differences in regime. Diffusion and induced trajectory evolution should be treated as a simultaneous phenomenon, and we contemplate that the framework sketched above will facilitate this difficult task.
7. Conclusions
The characteristics framework presented in this paper can help to make progress towards the difficult problem of measuring the output of technology. The evaluation of both the effectiveness of industrial and technology policies and of the contribution of technological change to economic development depend on the solution of this problem. Thus, for example, the effectiveness of R&D policies does in the end depend on the quality and quantity of the technical change that they bring about. No claim is made to have solved the problem of measuring the output of technology. On the contrary in this paper it is assumed that no perfect indicator of technological output is either available at the moment or is likely to be developed. A plurality of indicators of technological output will be required and in this paper it is hoped to provide
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a framework that could accommodate more than one type of indicator. The characteristics framework adopted in this paper should be useful both for the collection and for the elaboration of data about the evolution of technologies.
References [1] OECD DSTI Secretariat, Patents, Invention and Innovation: A review of the papers presented at the June 1982 Workshop on patent and innovation statistics, DSTI/SPR/82/74 (OECD, Paris, 1982). [2] K.J. Lancaster, A New Approach to Consumer Theory, Journal of Political Economy 14 (1966) 133-156. [3] Z. Griliehes (Ed.), Price lndexes and Quality Change (Harvard University Press, Cambridge, 1971). [4] E. Layton, Technology as Knowledge, Technology and Culture 15 (1972) 31-41. [5] ASTME (American Society of Tool and Manufacturing Engineers), Value Engineering in Manufacturing (Prentice Hall, Englewood Cliffs, 1967). [6] R.R. Nelson and S.G. Winter, In Search of Useful Theory of Innovation, Research Policy 6 (1977) 36-76. [7] D, Sahal, Alternative Conceptions of Technology, Research Policy 10 (1981) 2-24. [8] W.J. Abernathy and J.M. Utterback, Patterns of Industrial Innovation, Technology Review 80 (1978) 41-47. [9] D. Mowery and N. Rosenberg, The Influence of Market Demand upon Innovation: a critical review of some recent empirical studies, Research Policy 8 (1979) 103-53. [10] P.P. Saviotti, P.C. Stubbs, R.W. Coombs and M. Gibbons, An Approach to the Construction of Indexes of Technological Sophistication, TechnologicalForecasting and Social Change 21 (1982) 133-147. [11] D. Sahal, A Theory of Measurement of Technological Change, International Journal of Systems Science 8 (1977) 671-682. [12] J. Schumpeter, The Theory of Economic Development (Harvard University Press, Cambridge, Mass., 1934). [13] H. Binswanger, A microeconomic Approach to Induced Innovation, Economic Journal 84 (1974) 940-58. [14] N. Rosenberg, Inside the Black Box (Cambridge University Press, Cambridge, 1982).
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Appendix Table 2 Product characteristics - agricultural tractor Technical characteristics Engine
Service characteristics Type (diesel, petrol) Size No. cylinders Bore Stroke Compression ratio Turbo compressor
Transmission
No, driving wheels No, forward gears Syncromesh Change on the move
Steering
Power steering
PTO
PTO presence No. PTO speeds PTO ( L / l )
Hydraulics
(L/I)
Main services
Economic environment (costs) Drawbar power Speed Fuel consumption
Complementary services External ities
Reliability Driver comfort
Safety Noise
Purchase price Depreciation Maintenance Running costs
P.P. Saviotti and J, S. Metcalfe / Technological output indicators Table 3 Product characteristics - plastic (PVC) pipes Technical characteristics Material
Service characteristics
Economic environment (costs)
Physical properties Specific gravity Natural coiour Clarity Colour possibili ties Odour Taste
Mechanical properties Tensile strength Elongation Bending strength Modulus of elasticity Compression strength Hardness (ball indentation)
Thermal properties Resistance to continuous heat Softening range Range of fusion • Temperature of thermal decomposition Flammability Brittle temperature Specific heat Thermal conductivity Thermal expansion
Electrical properties Volumetric resistivity Surface resistivity Dielectric constant Power factor Resistivity breakdown voltage
Physical/chemical properties Effect of aging Effect of light Weather resistance Resistance to boiling water Water absorption (24 h) Water vapour permeability Effects of acids: weak strong Effect of alkalies: weak strong Effect of organic solvents: Soluble in Swells in Resists Pipe
Outside diameter Inside diameter Colour Length Tolerance
Flow rate Max. pressure Burst rate Weight Corrosion resistance Average lifetime
Purchase Transportation Installation Maintenance
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