cumulative papers N , cumulativecitations L i of an individual paper i and cumulativecitations L sum of all papers of an author. The former two cases are examples of individual systems, whereas the last one is an example of a collective of systems
relationship between the fraction α ( t ) of items and their maximum value C i.e. L ( t ) = Cα ( t ) and Δ L ( t ) = C Δ α ( t ), Eqs. 3 and 7 may be written in the form:
For the analysis of real data on the dependence of cumulativecitations
Based on the transfer function model of the observed citation distribution and the expression of the cumulative citation probability
distribution, parameters of 12 citation distributions are identified from statistical data of age distributions of references
of 10 journals in JCR using the parameter optimization fitting method. At same time, based on the steady state solution of
differential equations of the publication delay process and data of publication delays of 10 journals, the publication delay
parameters of every journal are identified using the fitting method. Identified parameters of every journal citation distribution
are compared with the journal’s publication delay parameters and some valuable conclusions are deduced.
This paper documents that salient features of (time series of annual) citations to scientific publications might be captured by a Bass type diffusion model. This is particularly useful as it allows for a comparison of these features across journals, across disciplines and over time. For the illustrative case of Econometrica 1987, it is found that the peak in citations occurs at 6.5 years, on average. Also, it is found that after 14 years there is only a little gap between cumulative citations and the estimated total cumulative amount, suggesting that on average the impact of these articles lasts for about 15 years or so. Finally, it appears that these features can partly be explained by the size of the articles, as it is found that longer papers get more citations and peak later.
Not all highly cited papers have the same citation life cycle curves, i.e. curves of frequency of citations received vs. time. The citation life of ten randomly selected Citation Classics, five in medicine and five in biochemistry, are studied longitudinally in time and compared with a random sample of ten non-classics of the same cohort. There are pronounced differences in the life cycle curves; two distinct types are suggested. Type A, comprised of both high and low cited papers in both fields, has an early peak of citation rate and may be approximated by a bilinear cumulative citation curve with a break at six years of age, when three quarters of the total number of citations have occurred. Type B, in this study comprised of extremely highly cited methodological Citation Classics, exhibit a constant or slowly accelerating growth rate with a vigorous citation life extending over the entire period studied and typically one third or less of the total citations accumulated at six years of age.
Authors:Weiwei Zhang, Weihong Qian, and Yuh-Shan Ho
This study is a bibliometric analysis on ocean circulation-related research for the period 1991–2005. Selected documents included
“ocean circulation, sea circulation, seas circulation, marine circulation, and circulation ocean” as a part of the title,
abstract or keywords. Analyzed parameters included the document type, the article output, the article distribution in journals,
the publication activity of countries, and institutes and the authorship. An indicator, citation per publication (CPP) was
applied to evaluate the scientific impact of a publication. The relationship between cumulative articles and the year was
modeled. Three dominant categories were picked out, and their output increase was modeled. The USA was found to be leading
the research with 47% share of total articles, with a CPP up to 5.9. Woods Hole Oceanography Institute in the USA was the
most productive institute with a CPP of 6.8. In the citation analysis, a 5th year citation mode was found. A paper life model
was applied to compare the cumulative citations increasing rates of different years.
According to the definition of reliability-based citation impact factor (R-impact factor) proposed by KUO & RUPE and the cumulative
citation age distribution model, a mathematical expression of the relationship between R-impact factor and impact factor is
established in this paper. By simulation of the change processes of the R-impact factor and impact factor in the manipulation
process of the impact factor, it is found that the effect of manipulation can be partly corrected by the R-impact factor in
some cases. Based on the Journal Citation Report database, impact factors of 4 normal journals and 4 manipulated journals
were collected. The journals’ R-impact factors and self-cited rates in the previous two years were calculated for each year
during the period 2000 to 2007, and various characteristics influenced by the manipulation were analyzed. We find that the
R-impact factor has greater fairness than the impact factor for journals with relatively short cited half-lives. Finally,
some issues about using the R-impact factor as a measure for evaluating scientific journals are discussed.
Self-citations — those where authors cite their own works — account for a significant portion of all citations. These self-references
may result from the cumulative nature of individual research, the need for personal gratification, or the value of self-citation
as a rhetorical and tactical tool in the struggle for visibility and scientific authority. In this article we examine the
incentives that underlie self-citation by studying how authors’ references to their own works affect the citations they receive
from others. We report the results of a macro study of more than half a million citations to articles by Norwegian scientists
that appeared in the Science Citation Index. We show that the more one cites oneself the more one is cited by other scholars.
Controlling for numerous sources of variation in cumulative citations from others, our models suggest that each additional
self-citation increases the number of citations from others by about one after one year, and by about three after five years.
Moreover, there is no significant penalty for the most frequent self-citers — the effect of self-citation remains positive
even for very high rates of self-citation. These results carry important policy implications for the use of citations to evaluate
performance and distribute resources in science and they represent new information on the role and impact of self-citations
in scientific communication.
Authors:Gerard Pasterkamp, Joris Rotmans, Dominique de Kleijn, and Cornelius Borst
Context. The use of citation frequency and impact factor as measures of research quality and journal prestige is being criticized.
Citation frequency is augmented by self-citation and for most journals the majority of citations originate from a minority
of papers. We hypothesized that citation frequency is also associated with the geographical origin of the research publication.
Objective. We determined whether citations originate more frequently from institutes that are located in the same country as the authors
of the cited publication than would be expected by chance.
Design. We screened citations referring to 1200 cardiovascular publications in the 7 years following their publication. For the
1200 citation recipient publications we documented the country where the research originated (9 countries/regions) and the
total number of received citations. For a selection of 8864 citation donor papers we registered the country/region where the
citing paper originated.
Results. Self-citation was common in cardiovascular journals (n = 1534, 17.8%). After exclusion of self-citation, however, the number
of citations that originated from the same country as the author of the citation recipient was found to be on average 31.6%
higher than would be expected by chance (p<0.01 for all countries/regions). In absolute numbers, nation oriented citation
bias was most pronounced in the USA, the country with the largest research output (p<0.001).
Conclusion. Citation frequency was significantly augmented by nation oriented citation bias. This nation oriented citation behaviour
seems to mainly influence the cumulative citation number for papers originating from the countries with a larger research
Authors:K. Satyanarayana, D. Srivastava, and V. Sreenivas
This study aims to examine whether rapid communications exert more influence/impact on subsequent research. Citation analysis
of Short Communications (SCs) and Main Articles (MAs) from 1983 and 1990 for 5 high impact biomedical journals was carried
out for a five year period following publication.
The mean citations cumulated for the five year period showed no consistent trend. Some journals showed more citations for
SCs while some showed more for MAs. The mean citations (range) for SCs and MAs for the 1983 and 1990 papers respectively were
as follows:Gene: 14.13 (0-61) and 38.79 (0-677), 9.73 (0-93) and 13.17 (0-44);Journal of Clinical Investigation (JCI): 79.77 (3-202) and 27.52 (0-86), 50.52 (0-254) and 33.53 (0-151);Journal of Experimental Medicine (JEM): 39.80 (0-200) and 49.20 (0-403), 47.26 (0-258) and 50.27 (0-173); andJournal of Biological Chemistry (JBC); 36.21 (0-380) and 19.67 (0-53), 37.19 (0-273) and 26.84 (0-185). SCs ofJournal of Cell Biology (JCB) had a mean citation of 25.84 per article with a range of 0-98, while the MAs had a mean citation of 33.13 with the
range 4-122 during 1983-87.
The citation peak was seen about three years after publication for all the journals during both the periods. The mean cumulative
citations showed a progressive increase over the five years for both types of papers, in all journals and for both the 5 year
periods. The initial differences observed persisted even four years after the year of publication. No significant differences
were observed in the distribution of the cumulative 5 year citations between the SCs and MAs. An index of speed of citation
per article showed no substantial differences between SCs and MAs with MAs showing an edge over SCs. Both MAs and SCs of all
the journals showed nearly same average time per citation per article further confirming that the SCs do not enjoy the advantage
of speedier citation.
The results show that the generally perceived feeling of SCs getting cited more frequently and faster does not appear to be
valid. Hence, the practice of publishing SCs on a priority basis is perhaps not warranted.