- Email: [email protected]
Journal Self-citation Analysis of Some Chinese Sci-tech Periodicals
Journal Self-citation Analysis of Some Chinese Sci-tech Periodicals Xia Xiao-dong and Wu Ya-wen Available online 30 July 2011 This study investigates self-citation rates of 222 Chinese journals within seven groups including 76 journals of agronomy (34.2 percent), 57 of biology (25.7 percent), 28 of environmental science and technology (12.6 percent), 15 of forestry (6.8 percent), 24 of academic journals of agricultural university (10.8 percent), 9 of aquatic sciences (4.1 percent), and 13 of animal husbandry and veterinary medicine (5.9 percent). The average self-citation rates range from 2 percent to 67 percent in 2006, 1 percent to 68 percent in 2007 and 0 percent to 67 percent in 2008. There is a significant difference in self-citation rate between most groups of journals. The self-citation rate is positively and significantly correlated with the self-citation rate in 2006 for all 222 journals (N = 222, R2 = 0.194, P = 0.004) (P b 0.05). However, the self-citation rate is not significantly correlated with the journal's impact factor in 2007 (N = 222, R2 = 0.114, P = 0.091) and 2008 (N = 222, R2 = 0.112, P = 0.096) (P b 0.05) for the 222 journals. The relationship between selfcitation rate and journal impact factor is discussed. Serials Review 2011; 37:171–173. © 2011 Elsevier Inc. All rights reserved.
Introduction
aquatic sciences and environmental science and technology from 2006 to 2008.
The journal impact factor is a widely used index for the evaluation of scientific influence and level of journals.1-4 However, its limitation is very obvious. The impact factor is not valid for the assessment of the quality of individual papers and the quality of individual scientists.5 The impact factor can be influenced and biased (intentionally or otherwise) by many factors.6 The journal impact factor is calculated by dividing the total number of citations that a journal receives over a period of 2 years by the number of articles it published in that same period. Thus, editors can manipulate the journal impact factor for better ranking of their journals by encouraging or requesting authors to cite articles in their journals.7-10 The risk of editors' manipulations to the journal impact is truly present, usually resulting in excessive journal self-citation. In this study the definition of “self-citation” rate for a journal is the ratio of a journal's self-citation to the number of times it is cited by all journals; it contrasts with the “self-citing” rate, which is the ratio of a journal's self-citation to the total citations it makes. In order to elucidate the relationship between the journal impact factor and journal self-citation, this study investigated the self-citation rates of 222 Chinese journals belonging to agronomy, biology, academic journals of agricultural university, forestry, animal husbandry and veterinary medicine,
Methods A total of 222 Chinese journals were selected. The data of selfcitation rates and impact factors of journals were obtained from Chinese Journal Citation Reports 2007, 2008 and 2009 (the data for 2006, 2007 and 2008 are available), which is published by the Institute of Scientific and Technical Information of China. The 222 Chinese journals were divided into seven groups, among which 76 belonged to agronomy (AG), covering 34.2 percent of the total; 57 percent to biology (B), occupying 25.7 percent; 28 percent to environmental science and technology (EST), 12.6 percent; 15 percent to forestry (F), 6.8 percent; 24 percent to academic journals of agricultural university (AJAU), 10.8 percent; 9 percent to aquatic sciences (AS), 4.1 percent; 13 percent to animal husbandry and veterinary medicine (AHVM), 5.9 percent. All data were analyzed by SPSS 13.0.
Results and Analysis Self-citation Rates of Selected Chinese Journals from 2006 to 2008 The average self-citation rates in the selected journals ranged from 0.02 to 0. 67 in 2006, 0.01 to 0.68 in 2007 and 0 to 0.67 in 2008 (see Fig. 1). The numbers of journals with a self-citation rate less than 10 percent were 89, 93 and 98 in 2006, 2007 and 2008, respectively. For those with a self-citation rate from 60 percent to 70 percent, the numbers were 2, 3 and 1 in 2006, 2007 and 2008, respectively. The average (mean ± SE) of self-citation rates for the selected journals from 2006 to 2008 were 0.1604 ± 0.1232, 0.1573 ± 0.1252,0.1537 ± 0.1195, respectively (see Table 1). This average
Xia is editor (assistant research fellow, master), Editorial Office, Chinese Journal of Rice Science, China National Rice Research Institute, Hangzhou 310006, China; e-mail: [email protected]. Wu is associate senior editor, master of biology, Chinese Journal of Rice Science, China National Rice Research Institute, Hangzhou 310006, China; e-mail: [email protected]. ACKNOWLEDGMENT: The research is supported by the Special Foundation for Central Academics of China (2009RG005-4). 0098-7913/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.serrev.2011.02.002
171
Xia Xiao-dong and Wu Ya-wen
Serials Review
100
Number of journals
Table 1. Self-citation rates of selected Chinese journals from 2006 to 2008.
2006
90
Self-citation rate (Mean ± SD)
80
Group
N
2006
2007
2008
70
EST F AJAU AG B AS AHVM Total
28 15 24 76 57 9 13 222
0.1539 ± 0.1573 0.2593 ± 0.1816 0.0867 ± 0.0461 0.1793 ± 0.1173 0.1226 ± 0.0841 0.1833 ± 0.1264 0.2354 ± 0.1137 0.1604 ± 0.1232
0.1675 ± 0.1601 0.2267 ± 0.1705 0.0754 ± 0.0371 0.1757 ± 0.1213 0.1153 ± 0.0851 0.2089 ± 0.1631 0.2485 ± 0.0981 0.1573 ± 0.1252
0.1739 ± 0.1674 0.1813 ± 0.1176 0.0696 ± 0.0469 0.1730 ± 0.1119 0.1125 ± 0.0774 0.1989 ± 0.1448 0.2692 ± 0.1297 0.1537 ± 0.1195
60 50 40 30 20
EST, environmental science and technology; F, forestry; AJAU, academic journals of agricultural university; AG, agronomy; B, biology; AS, aquatic sciences; AHVM, animal husbandry and veterinary medicine.
10 0
0
10
20
30
40 50 60 70 Self-citation rate/%
80
90
100
P = 0.004). However, the self-citation rate was not significantly correlated with the journal's impact factor in 2007 (N = 222, R2 = 0.114, P = 0.091) and 2008 (N = 222, R2 = 0.112, P = 0.096) for all the journals (see Fig. 2).
100 2007
90
Number of journals
80 70 60
Discussion
50
The impact factor has played an increasingly vital role in the evaluation of a journal's scientific level. A high self-citation rate may arise from a journal's having a novel or highly specific topic for which it provides a unique publication venue. It may also result from the journal having few incoming citations from other sources. Journal self-citation might also be affected by sociological factors in the practice of citation. Researchers will cite journals of which they are most aware; this is roughly the same population of journals to which they will consider sending their own papers for review and publication. It is also possible that self-citation derives from an editorial practice of the journal. To achieve a relatively higher impact factor, self-citation might be encouraged and even requested by some editors, resulting in a higher self-citation rate. Such scientific misconduct might lessen the value of citation analysis. In this study, the average self-citation rates of the 222 selected journals from 2006 to 2008 were 0.1604 ± 0.1232, 0.1573 ± 0.1252 and 0.1537 ± 0.1195, respectively, without a significant difference among them. However, it seems to follow a descending trend year by year. This is consistent with the results of Xue-li Liu and Mei-ying Wang.11 However, the self-citation rates of the 222 journals from 2006 to 2008 are higher than those calculated by Liu and Wang. Liu and Wang investigated the self-citation rates of Chinese biomedical journals. They found that the average self-citation rates of these journals for the years 2005–2007 showed a downward trend and set the upper limits of normal values of self-citation rates for the same period.12 The standard deviation of self-citation rates are 0.1232, 0.1252 and 0.1195 in these years, representing the large
40 30 20 10 0
0
10
20
30
100
40 50 60 70 Self-citation rate/%
80
90
100
80
90
100
2008
90 Number of journals
80 70 60 50 40 30 20 10 0
0
10
20
30
40 50 60 70 Self-citation rate/%
Figure 1. Frequency distribution of self-citation rate of selected journals in 2006–2008.
showed a downward trend without significant difference. In 2006, the highest self-citation rate occurred in F group journals (0.2593 ± 0.1816). In 2007, AHVM group journals showed the highest self-citation rate among the seven groups (0.2485 ± 0.0981). In 2008, the self-citation rate of AHVM group journals was the highest (0.2692 ± 0.1297). The self-citation rates in AG from 2006 to 2008 were significantly higher than those of B and AJAU group journals (see Table 2). Groups with n b 20 are excluded in the statistical comparison.
Table 2. Comparisons of self-citation rates between each paired group in 2006(upper), 2007(middle) and 2008(bottom) (P values)
EST
AJAU
AJAU
AG
B
0.038 0.005 0.001
0.323 0.754 0.971 0.001 0.000 0.000
0.243 0.055 0.017 0.204 0.165 0.114 0.006 0.004 0.002
Correlation between Self-citation Rate and Impact Factor
AG
The self-citation rate was positively correlated with the journal's impact factor in 2006 for all the 222 journals (N = 222, R2 = 0.194,
P b 0.05 indicate a significant difference in self-citation rates between two groups. P values for self-citation rates of groups with n b 20 are not showed.
172
Volume 37, Number 3, 2011
0.80
Journal Self-citation Analysis of Some Chinese Sci-tech Periodicals
Though the impact factor has long been a good index to rank the scientific influence and level of journals, it is time to explore newer indices for journal ranking, such as the Eigenfactor, which possibly are less subject to manipulation. Hirsch proposed to rank authors according to the H-index.13 The G-index (a modification of the H-index) was proposed by Leo Egghe and others.14,15 Journal eigenvector centrality was proposed to rank journals.16 Journal citation PageRank was proposed to rank journals17,18 and individual articles.19
2006 N=222, R2=0.194, P=0.004
0.70
Self-citation
0.60 0.50 0.40 0.30 0.20 0.10
Notes
0.00 1.00 0.90
N=222, R2=0.114, P=0.091
0.80 0.70 self-citation
1.
Richard Hobbs, “Should We Ditch Impact Factors,” British Medical Journal 334, no. 7593 (March 2007): 569.
2.
Eugene Garfield, “The History and Meaning of the Journal Impact Factor,” The Journal of the American Medical Association 295 no. 1 (January 2006): 90–93.
3.
David Adam, “Citation Analysis: The Counting House,” Nature 415, no. 6873 (February 2002): 726–729.
4.
Rajna Golubic, Mihael Rudes, Natasa Kovacic, Matko Marusic and Ana Marusic, “Calculating Impact Factor: How Bibliographical Classification of Journal Items Affects the Impact Factor of Large and Small Journals,” Science and Engineering Ethics 14, no. 1 (March 2008): 41–49.
5.
Tobias Opthof, “Sense and Nonsense about the Impact Factor,” Cardiovascular Research 33, no. 1 (January 1997): 1–7.
6.
Andrew P. Kurmis, “Current Concepts Review: Understanding the Limitations of the Journal Impact Factor,” Journal of Bone and Joint Surgery 85, no. 12 (December 2003): 2449–2454.
7.
Charles Jennings, “Citation Data: The Wrong Impact,” Nature Neuroscience 1, no. 8 (December 1998): 641–642.
8.
Jeffrey Boone Miller, “Impact Factors and Publishing Research,” Scientist 16, no. 18 (September 2002): 11.
9.
James Neuberger and Christopher Counsell, “Impact Factors: Uses and Abuses,” European Journal of Gastroenterology and Hepatology 14, no. 3 (March 2002): 209–211.
10.
Alper Sevinc, “Manipulating Impact Factor: An Unethical Issue or an Editor's Choice,” Swiss Medical Weekly 134, no. 27-28 (July 2004): 410.
11.
Xue-li Liu and Mei-ying Wang, “Self-citation in Chinese Biomedical Journals,” Learned Publishing 23, no. 2 (April 2010): 93–100.
12.
Ibid.
13.
J. E. Hirsch, “An Index to Quantify an Individual's Scientific Research Output,” Proceedings of the National Academy of Sciences 102, no. 46 (November 2005): 16569–16572.
14.
Jin BiHui, Liang Liming, Ronald Rousseau and Leo Egghe, “The R- and ARindices: Complementing the H-index,” Chinese Science Bulletin 52, no. 6 (March 2007): 855–863.
15.
Leo Egghe, “Theory and practice of the g-index,” Scientometrics 69, no. 1 (April 2006): 131–152.
16.
Gabriel Pinski and Francis Narin, “Citation Influence for Journal Aggregates of Scientific Publications: Theory, with Application to the Literature of Physics,” Information Processing and Management 12, no. 5 (1976): 297–312.
17.
Johan Bollen, Marko A. Rodriguez and Herbert Van de Sompel, “Journal Status,” Scientometrics 69, no. 3 (December 2006): 669–687.
18.
Robert P. Dellavalle, Lisa M. Schilling, Marko A. Rodriguez, Herbert Van de Sompel and Johan Bollen, “Refining Dermatology Journal Impact Factors using PageRank,” Journal of the American Academy of Dermatology 57, no. 1 (May 2007): 116–119.
19.
P. Chen, H. Xie, S. Maslov and S. Redner, “Finding Scientific Gems with Google's PageRank Algorithm,” Journal of Informetrics 1, no. 1 (January 2007): 8–15.
2007
0.60 0.50 0.40 0.30 0.20 0.10 0.00 0.0
0.5
1.0
1.00
1.5
2.0
2008
0.90
2
N=222, R =0.112, P=0.096
0.80 Self-citation
0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 0.0
0.5
1.0
1.5 Impact factor
2.0
2.5
3.0
Figure 2. Correlation between impact factor and self-citation rate of selected journals from 2006 to 2008. P b 0.05 indicate a significant difference in self-citation rates between two groups.
variation of self-citation of the journals. In our study, F group journals (0.2593 ± 0.1816), AHVM group journals (0.2485 ± 0.0981) and AHVM group journals (0.2692±0.1297) showed the highest selfcitation rate in 2006, 2007 and 2008, respectively. In this study, the self-citation rate was positively and significantly correlated with the journal's impact factor in 2006 for all 222 journals. However, the self-citation rate was not significantly correlated with the journal's impact factor in 2007 and 2008. Perhaps in 2007 and 2008, editors became more rational in the treatment of citation for their journals. Self-citation should not be encouraged and requested; however, a certain amount of selfcitation is reasonable and necessary.
173
Introduction
aquatic sciences and environmental science and technology from 2006 to 2008.
The journal impact factor is a widely used index for the evaluation of scientific influence and level of journals.1-4 However, its limitation is very obvious. The impact factor is not valid for the assessment of the quality of individual papers and the quality of individual scientists.5 The impact factor can be influenced and biased (intentionally or otherwise) by many factors.6 The journal impact factor is calculated by dividing the total number of citations that a journal receives over a period of 2 years by the number of articles it published in that same period. Thus, editors can manipulate the journal impact factor for better ranking of their journals by encouraging or requesting authors to cite articles in their journals.7-10 The risk of editors' manipulations to the journal impact is truly present, usually resulting in excessive journal self-citation. In this study the definition of “self-citation” rate for a journal is the ratio of a journal's self-citation to the number of times it is cited by all journals; it contrasts with the “self-citing” rate, which is the ratio of a journal's self-citation to the total citations it makes. In order to elucidate the relationship between the journal impact factor and journal self-citation, this study investigated the self-citation rates of 222 Chinese journals belonging to agronomy, biology, academic journals of agricultural university, forestry, animal husbandry and veterinary medicine,
Methods A total of 222 Chinese journals were selected. The data of selfcitation rates and impact factors of journals were obtained from Chinese Journal Citation Reports 2007, 2008 and 2009 (the data for 2006, 2007 and 2008 are available), which is published by the Institute of Scientific and Technical Information of China. The 222 Chinese journals were divided into seven groups, among which 76 belonged to agronomy (AG), covering 34.2 percent of the total; 57 percent to biology (B), occupying 25.7 percent; 28 percent to environmental science and technology (EST), 12.6 percent; 15 percent to forestry (F), 6.8 percent; 24 percent to academic journals of agricultural university (AJAU), 10.8 percent; 9 percent to aquatic sciences (AS), 4.1 percent; 13 percent to animal husbandry and veterinary medicine (AHVM), 5.9 percent. All data were analyzed by SPSS 13.0.
Results and Analysis Self-citation Rates of Selected Chinese Journals from 2006 to 2008 The average self-citation rates in the selected journals ranged from 0.02 to 0. 67 in 2006, 0.01 to 0.68 in 2007 and 0 to 0.67 in 2008 (see Fig. 1). The numbers of journals with a self-citation rate less than 10 percent were 89, 93 and 98 in 2006, 2007 and 2008, respectively. For those with a self-citation rate from 60 percent to 70 percent, the numbers were 2, 3 and 1 in 2006, 2007 and 2008, respectively. The average (mean ± SE) of self-citation rates for the selected journals from 2006 to 2008 were 0.1604 ± 0.1232, 0.1573 ± 0.1252,0.1537 ± 0.1195, respectively (see Table 1). This average
Xia is editor (assistant research fellow, master), Editorial Office, Chinese Journal of Rice Science, China National Rice Research Institute, Hangzhou 310006, China; e-mail: [email protected]. Wu is associate senior editor, master of biology, Chinese Journal of Rice Science, China National Rice Research Institute, Hangzhou 310006, China; e-mail: [email protected]. ACKNOWLEDGMENT: The research is supported by the Special Foundation for Central Academics of China (2009RG005-4). 0098-7913/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.serrev.2011.02.002
171
Xia Xiao-dong and Wu Ya-wen
Serials Review
100
Number of journals
Table 1. Self-citation rates of selected Chinese journals from 2006 to 2008.
2006
90
Self-citation rate (Mean ± SD)
80
Group
N
2006
2007
2008
70
EST F AJAU AG B AS AHVM Total
28 15 24 76 57 9 13 222
0.1539 ± 0.1573 0.2593 ± 0.1816 0.0867 ± 0.0461 0.1793 ± 0.1173 0.1226 ± 0.0841 0.1833 ± 0.1264 0.2354 ± 0.1137 0.1604 ± 0.1232
0.1675 ± 0.1601 0.2267 ± 0.1705 0.0754 ± 0.0371 0.1757 ± 0.1213 0.1153 ± 0.0851 0.2089 ± 0.1631 0.2485 ± 0.0981 0.1573 ± 0.1252
0.1739 ± 0.1674 0.1813 ± 0.1176 0.0696 ± 0.0469 0.1730 ± 0.1119 0.1125 ± 0.0774 0.1989 ± 0.1448 0.2692 ± 0.1297 0.1537 ± 0.1195
60 50 40 30 20
EST, environmental science and technology; F, forestry; AJAU, academic journals of agricultural university; AG, agronomy; B, biology; AS, aquatic sciences; AHVM, animal husbandry and veterinary medicine.
10 0
0
10
20
30
40 50 60 70 Self-citation rate/%
80
90
100
P = 0.004). However, the self-citation rate was not significantly correlated with the journal's impact factor in 2007 (N = 222, R2 = 0.114, P = 0.091) and 2008 (N = 222, R2 = 0.112, P = 0.096) for all the journals (see Fig. 2).
100 2007
90
Number of journals
80 70 60
Discussion
50
The impact factor has played an increasingly vital role in the evaluation of a journal's scientific level. A high self-citation rate may arise from a journal's having a novel or highly specific topic for which it provides a unique publication venue. It may also result from the journal having few incoming citations from other sources. Journal self-citation might also be affected by sociological factors in the practice of citation. Researchers will cite journals of which they are most aware; this is roughly the same population of journals to which they will consider sending their own papers for review and publication. It is also possible that self-citation derives from an editorial practice of the journal. To achieve a relatively higher impact factor, self-citation might be encouraged and even requested by some editors, resulting in a higher self-citation rate. Such scientific misconduct might lessen the value of citation analysis. In this study, the average self-citation rates of the 222 selected journals from 2006 to 2008 were 0.1604 ± 0.1232, 0.1573 ± 0.1252 and 0.1537 ± 0.1195, respectively, without a significant difference among them. However, it seems to follow a descending trend year by year. This is consistent with the results of Xue-li Liu and Mei-ying Wang.11 However, the self-citation rates of the 222 journals from 2006 to 2008 are higher than those calculated by Liu and Wang. Liu and Wang investigated the self-citation rates of Chinese biomedical journals. They found that the average self-citation rates of these journals for the years 2005–2007 showed a downward trend and set the upper limits of normal values of self-citation rates for the same period.12 The standard deviation of self-citation rates are 0.1232, 0.1252 and 0.1195 in these years, representing the large
40 30 20 10 0
0
10
20
30
100
40 50 60 70 Self-citation rate/%
80
90
100
80
90
100
2008
90 Number of journals
80 70 60 50 40 30 20 10 0
0
10
20
30
40 50 60 70 Self-citation rate/%
Figure 1. Frequency distribution of self-citation rate of selected journals in 2006–2008.
showed a downward trend without significant difference. In 2006, the highest self-citation rate occurred in F group journals (0.2593 ± 0.1816). In 2007, AHVM group journals showed the highest self-citation rate among the seven groups (0.2485 ± 0.0981). In 2008, the self-citation rate of AHVM group journals was the highest (0.2692 ± 0.1297). The self-citation rates in AG from 2006 to 2008 were significantly higher than those of B and AJAU group journals (see Table 2). Groups with n b 20 are excluded in the statistical comparison.
Table 2. Comparisons of self-citation rates between each paired group in 2006(upper), 2007(middle) and 2008(bottom) (P values)
EST
AJAU
AJAU
AG
B
0.038 0.005 0.001
0.323 0.754 0.971 0.001 0.000 0.000
0.243 0.055 0.017 0.204 0.165 0.114 0.006 0.004 0.002
Correlation between Self-citation Rate and Impact Factor
AG
The self-citation rate was positively correlated with the journal's impact factor in 2006 for all the 222 journals (N = 222, R2 = 0.194,
P b 0.05 indicate a significant difference in self-citation rates between two groups. P values for self-citation rates of groups with n b 20 are not showed.
172
Volume 37, Number 3, 2011
0.80
Journal Self-citation Analysis of Some Chinese Sci-tech Periodicals
Though the impact factor has long been a good index to rank the scientific influence and level of journals, it is time to explore newer indices for journal ranking, such as the Eigenfactor, which possibly are less subject to manipulation. Hirsch proposed to rank authors according to the H-index.13 The G-index (a modification of the H-index) was proposed by Leo Egghe and others.14,15 Journal eigenvector centrality was proposed to rank journals.16 Journal citation PageRank was proposed to rank journals17,18 and individual articles.19
2006 N=222, R2=0.194, P=0.004
0.70
Self-citation
0.60 0.50 0.40 0.30 0.20 0.10
Notes
0.00 1.00 0.90
N=222, R2=0.114, P=0.091
0.80 0.70 self-citation
1.
Richard Hobbs, “Should We Ditch Impact Factors,” British Medical Journal 334, no. 7593 (March 2007): 569.
2.
Eugene Garfield, “The History and Meaning of the Journal Impact Factor,” The Journal of the American Medical Association 295 no. 1 (January 2006): 90–93.
3.
David Adam, “Citation Analysis: The Counting House,” Nature 415, no. 6873 (February 2002): 726–729.
4.
Rajna Golubic, Mihael Rudes, Natasa Kovacic, Matko Marusic and Ana Marusic, “Calculating Impact Factor: How Bibliographical Classification of Journal Items Affects the Impact Factor of Large and Small Journals,” Science and Engineering Ethics 14, no. 1 (March 2008): 41–49.
5.
Tobias Opthof, “Sense and Nonsense about the Impact Factor,” Cardiovascular Research 33, no. 1 (January 1997): 1–7.
6.
Andrew P. Kurmis, “Current Concepts Review: Understanding the Limitations of the Journal Impact Factor,” Journal of Bone and Joint Surgery 85, no. 12 (December 2003): 2449–2454.
7.
Charles Jennings, “Citation Data: The Wrong Impact,” Nature Neuroscience 1, no. 8 (December 1998): 641–642.
8.
Jeffrey Boone Miller, “Impact Factors and Publishing Research,” Scientist 16, no. 18 (September 2002): 11.
9.
James Neuberger and Christopher Counsell, “Impact Factors: Uses and Abuses,” European Journal of Gastroenterology and Hepatology 14, no. 3 (March 2002): 209–211.
10.
Alper Sevinc, “Manipulating Impact Factor: An Unethical Issue or an Editor's Choice,” Swiss Medical Weekly 134, no. 27-28 (July 2004): 410.
11.
Xue-li Liu and Mei-ying Wang, “Self-citation in Chinese Biomedical Journals,” Learned Publishing 23, no. 2 (April 2010): 93–100.
12.
Ibid.
13.
J. E. Hirsch, “An Index to Quantify an Individual's Scientific Research Output,” Proceedings of the National Academy of Sciences 102, no. 46 (November 2005): 16569–16572.
14.
Jin BiHui, Liang Liming, Ronald Rousseau and Leo Egghe, “The R- and ARindices: Complementing the H-index,” Chinese Science Bulletin 52, no. 6 (March 2007): 855–863.
15.
Leo Egghe, “Theory and practice of the g-index,” Scientometrics 69, no. 1 (April 2006): 131–152.
16.
Gabriel Pinski and Francis Narin, “Citation Influence for Journal Aggregates of Scientific Publications: Theory, with Application to the Literature of Physics,” Information Processing and Management 12, no. 5 (1976): 297–312.
17.
Johan Bollen, Marko A. Rodriguez and Herbert Van de Sompel, “Journal Status,” Scientometrics 69, no. 3 (December 2006): 669–687.
18.
Robert P. Dellavalle, Lisa M. Schilling, Marko A. Rodriguez, Herbert Van de Sompel and Johan Bollen, “Refining Dermatology Journal Impact Factors using PageRank,” Journal of the American Academy of Dermatology 57, no. 1 (May 2007): 116–119.
19.
P. Chen, H. Xie, S. Maslov and S. Redner, “Finding Scientific Gems with Google's PageRank Algorithm,” Journal of Informetrics 1, no. 1 (January 2007): 8–15.
2007
0.60 0.50 0.40 0.30 0.20 0.10 0.00 0.0
0.5
1.0
1.00
1.5
2.0
2008
0.90
2
N=222, R =0.112, P=0.096
0.80 Self-citation
0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 0.0
0.5
1.0
1.5 Impact factor
2.0
2.5
3.0
Figure 2. Correlation between impact factor and self-citation rate of selected journals from 2006 to 2008. P b 0.05 indicate a significant difference in self-citation rates between two groups.
variation of self-citation of the journals. In our study, F group journals (0.2593 ± 0.1816), AHVM group journals (0.2485 ± 0.0981) and AHVM group journals (0.2692±0.1297) showed the highest selfcitation rate in 2006, 2007 and 2008, respectively. In this study, the self-citation rate was positively and significantly correlated with the journal's impact factor in 2006 for all 222 journals. However, the self-citation rate was not significantly correlated with the journal's impact factor in 2007 and 2008. Perhaps in 2007 and 2008, editors became more rational in the treatment of citation for their journals. Self-citation should not be encouraged and requested; however, a certain amount of selfcitation is reasonable and necessary.
173