In Alves et al. (2014), we analyzed only the distribution of the first significant digit of the number of articles published of journals indexed in the JCR from 2007 to 2011. In this study, we extend our analysis to the second significant digit, and we investigate several other bibliometric indicators listed in the JCR from 2007 to 2014. In Fig. 2 we present a summary of our analysis. In the case of the number of articles, there is a small difference in relation to the values presented in Alves et al. (2014) because we considered now a larger number of decimal places in the calculation of the Chi square values. However, this difference did not affect the compliance (or not compliance) with BL in relation to our previous work.
According to all 288 tests performed, it is possible to observe that 191 (66.32 %) do not comply with BL. The result for each edition of the JCR is almost equal, 95 (65.97 %) for Science Edition and 96 (66.67 %) for Social Sciences Edition. By considering 1BL, 112 (77.78 %) do not comply with BL, while for 2BL 79 (54.86 %) do not comply with BL, which is a better result.
The average percentage of journals considered varied from an indicator to another. For instance, the total number of articles to the Science Edition is 97.82 % of the total number of journals for 1BL and 96.40 % for 2BL. For the Social Sciences Edition, the average percentage is very similar, 97.86 % for 1BL and 95.50 % for 2BL. The percentages are similar for the citations, self-citations, 2Y-IF, 2Y-IFWSC, 5Y-IF and immediacy index. However, for the cited and citing half-life the percentages are smaller than 77 % in the Science Edition and smaller than 63 % in the Social Sciences Edition.
Number of articles
Campanario and Coslado (2011) noted that the number of articles published in journals indexed in the JCR Science Edition do not comply with 1BL from 1998 to 2007. Alves et al. (2014) also noted the same in journals indexed in the JCR Science and Social Sciences Editions from 2007 to 2011. The same occurred from 2007 to 2014, but for the 2BL, some Chi square values in some years are smaller than the critical value. For instance, only 2 years (2007 and 2011) do not comply in the JCR Science Edition.
The number of articles published in a journal varies a little from 1 year to another, since the number of issues in a journal seldom changes yearly. This may explain the non-compliance of the first digit and the slight improvement on the second digit for the number of articles published.
We also investigated the journals according to their country of origin and to their JCR category. In Fig. 3 we present the percentage of countries and journal’s categories that complies with 1BL and 2BL considering the Chi square values for the number of articles published in journals indexed in the JCR Science and Social Sciences Editions from 2007 to 2014. The results for the 1BL are generally very good, for 2BL the results are always better than 1BL. An outlier occurred for the 1BL in the journal’s category in the JCR Social Sciences Edition. In this case, the average percentage is 52.52 % for 1BL and 93.04 % for 2BL.
Citation
The number of citations indicate the total number of times that each journal was cited by all journals included in the database within the current JCR year. For this indicator we observed that almost all data complies with 1BL, being the result still better for 2BL, that has a sole exception of non-compliance in the year 2012. Considering the self-citations, all years comply with 2BL. We also considered the number of citations without self-citations and to 2BL they all comply with BL. For the 1BL, non-compliance was observed in the years from 2009 to 2011 in the Science Edition. In 2009 and 2010, the Chi square values are smaller compared to those of the indicator with self-citations; nevertheless, they do not obey BL.
Considering the country of origin and the journal’s category for the citations and self-citations, both 1BL and for 2BL have a very high average acceptance percentage, around of 95 %, for the two JCR editions. For all cases, except by a small difference the journal’s category in Social Sciences Edition for self-citations, the percentage is higher for 2BL compared to 1BL.
Impact factor
The IF identifies the frequency with which an average article from a journal receives citations by other articles in a particular period. To 2Y-IF, the last 2 years are considered and for the 5Y-IF the last 5 years. To the IF values we noticed that almost all of them do not follow 1BL, expect the year 2007 in the Social Sciences Edition for 2Y-IFWSC. Additionally, the 5Y-IF do not follow 1BL, but it follows the 2BL, except in 2008 in the Social Sciences Edition. This is interesting since neither 2Y-IF nor 2Y-IFWSC follow BL in almost all years. It provides support for the preferential use of the 5Y-IF over the 2Y-IF or 2Y-IFWSC.
In Fig. 4 we present the percentage of countries and journal’s categories that complies with 1BL and 2BL considering the Chi square values for the impact factors in journals indexed in the JCR from 2007 to 2014. It is possible to observe that there is a significant difference from 2BL to 1BL in all cases, with an overall average percentage for compliance with 2BL around 95 %.
Half-life and immediacy
The cited half-life gives the number of years back from the current year that accounts for 50 % of the total number of citations to a journal. The citing half-life identifies the number of years from the current year that accounts for 50 % of the cited references from articles published by a journal. The immediacy index measures how frequently, in average, an article from a journal is cited within the same year of publication and it is a useful metrics for evaluating journals that publish cutting-edge research.
We noted that not all years of the cited and citing half-life indicators comply with 1BL and 2BL for the two JCR editions. We expect that the great majority of half-life values “>10.0” is probably bounded from 10 to 20 years. For the sake of calculation we, therefore, assumed “1” to be the first digit of all the half-life values “>10.0”. The new Chi square values obtained are slightly smaller but the conclusions for the first digit remain the same.
For the immediacy indicator the same pattern occurred with 2BL, but to 1BL, the Chi square values are in accordance to BL for some years.
It is worth noting the differences in percentage of compliance of 1BL and 2BL of cited and citing half-life by country and journal’s categories shown in Fig. 5. We observed 1BL smaller than 1 % in some cases, while for the 2BL the percentage stays around 90 %. To the immediacy index, the average percentage is around of 90 % for the 1BL and 95 % for the 2BL, except in journal’s categories in the JCR Social Sciences Edition that the average percentages are the opposite, that is, around 95 % for 1BL and 90 % for the 2BL.
Z-statistic
We used the Z-statistic to test each digit proportion separately, since it allows the identification of which ones may need further investigation. To 1BL, the result is that the Z values of almost all digits are greater than the cutoff level (1.96) for all bibliometric indicators but to citation and self-citations. Figure 6 presents the result to 2BL to all bibliometric indicators considered in this study. Observe that for digits 0 and 9, in almost all years, the values are greater than the cutoff value.