International Journal of Management Science and Business Administration
Volume 1, Issue 3, February 2015, Pages 6 -16
Does a Long Reference List Guarantee More Citations? Analysis of Malaysian Highly Cited and Review Papers
1Nader Ale Ebrahim, 2H. Ebrahimian, 3Maryam Mousavi, 4Farzad Tahriri
1Research Support Unit, Centre of Research Services, Institute of Research Management and Monitoring (IPPP), University of Malaya, Malaysia
2Institute of Mathematical Sciences, Faculty Science, University Malaya
3 4Centre for Product Design and Manufacturing, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603, Kuala Lumpur, Malaysia
Abstract: Earlier publications have shown that the number of references as well as the number of received citations are field-dependent. Consequently, a long reference list may lead to more citations. The purpose of this article is to study the concrete relationship between number of references and citation counts. This article tries to find an answer for the concrete case of Malaysian highly cited papers and Malaysian review papers. Malaysian paper is a paper with at least one Malaysian affilation. A total of 2466 papers consisting of two sets, namely 1966 review papers and 500 highly-cited articles, are studied. The statistical analysis shows that an increase in the number of references leads to a slight increase in the number of citations. Yet, this increase is not statistically significant. Therefore, a researcher should not try to increase the number of received citations by artificially increasing the number of references.
Key words: H-index, Citation analysis, Bibliometrics, Impact factor, Performance evaluation, Relations between citations and references
Researchers seeking citation tracking to find the most influential articles for a particular topic and to see how often their own published papers are cited (Bakkalbasi et al. 2006). On the other hand universities are looking for citations because of its influence in the university ranking (Ale Ebrahim et al. 2013, Ioannidis 2010, Bornmann, Leydesdorff, and Wang 2014). A citation count is the number of times a research work such as a journal article is cited by other works. The citation per paper meaningfully influence a number of metrics, including total citation counts, citation speed, the ratio of external to internal cites, diffusion scores and h-index (Carley, Porter, and Youtie 2013). Citation counts still commonly use for the measure of research papers quality and reputation (Abt and Garfield 2002). The number of citations that an article receives measured its impact on a specific field (Lai, Darius, and Lerut 2012). Citation analysis is one of the most important tools to evaluate research performance (Bornmann et al. 2012). Citation indicator is important for scientists and universities in all over the world (Farhadi, Salehi, Yunus, et al. 2013). In the early stage, the relationship between the number of references and the number of the paper citation was investigated in the 1965 (UZUN 2006, de Solla Price 1965). A long reference list at the end of a research paper may be the key to ensuring that it is well cited (Corbyn 2010, Ball 2008). Hence, citation counts are correlated with reference frequencies (Abt and Garfield 2002). Webster, Jonason, and Schember (2009) raised the question “Does the number of references an article contains predict its citation count?” and found that reference counts explained 19% of the variance in the citation counts. Lancho-Barrantes, Guerrero-Bote, and Moya-Anegón (2010) found that not only the number, but also the citation impact of the cited references correlated with the citation counts for a paper. The higher the impact of the cited references, the higher the later impact of the citing paper (Bornmann et al. 2012). Review articles are usually highly cited compare to other types of papers (Meho 2007).
Review papers represent the existing knowledge in a given field and more likely to be cited (Alimohammadi and Sajjadi 2009). Several bibliometric studies highlighted that citation counts are a function of many factors besides the scientific quality (Bornmann et al. 2012), length of paper (Abt and Garfield 2002), visibility (Ale Ebrahim et al. 2014), optimize scholarly literature for academic search engines (Beel, Gipp, and Wilde 2010), add the name of study in the title of all publications (Sarli and Holmes 2011), publishing in a journal with higher impact factor (Vanclay 2013), internet usage (Farhadi, Salehi, Embi, et al. 2013), gross domestic product (GDP) (Gholizadeh et al. 2014), number of authors (Krause 2009), self-archiving (Gargouri et al. 2010), publish in an open access journal (Swan 2010), collaborate with international authors (Pislyakov and Shukshina 2012), write paper with a Nobel laureates (Ball 2011) and many other (Ale Ebrahim et al. 2013) including write a review paper (Vanclay 2013) and use more references (Corbyn 2010). In this study the relationship between number of references and citation counts is determined. Webster, Jonason, and Schember (2009) mentioned “On average, review articles actually showed less of the relationship than standard articles” (Corbyn 2010). So, in this research both review and standard articles (papers) were investigated. 2466 articles consist of 1966 Malaysian review and 500 highly cited papers were selected to examine the relationship between number of references and citation counts in the given article.
2. Materials and methods
All data were obtained through Web of Science online academic database provided by Thomson Scientific. This database included the necessary information to examine the relationship between reference and citation counts for every review and highly cited papers published in Malaysia since 1980 to October 2013. Science Citation Index Expanded, Social Sciences Citation Index and Arts & Humanities Citation Index, were searched for reviews and highly cited papers. For each paper, all Bibliometrics data, especially the number of references and the number of times the paper has been cited during the interval between the year of publication and the year 2013, have been collected.Two samples set were selected: 1- The sample number one consisted of 1966 review papers in all disciplines from Malaysia, according to the Web of Knowledge’s classification system. Citation statistics produced by shorter than three years’ time frame may not be sufficiently stable (Adams 2005, UZUN 2006). Because, papers appearing in the Web of Science databases over the last few years, have not had enough time to accumulate a stable number of citations (Webster, Jonason, and Schember 2009). Therefore, the time span limited from 1980 to November, 2010; yielding a subsample of 721 publications (37% of the original sample). Publications with zero citation were removed. In order to select the highly cited paper a threshold 10 times cited per year is considered. The association between the number of references (independent variable) and time cited per year (dependent variable) of highly cited review papers investigated with linear and non-linear models. 2- The sample number two comprises 500 highly cited publications from Malaysia. According to the Web Of Science classification, the results are obtained based on the article type and exclude the review articles, editorial material, conference papers and book review.
3. Results and discussion
Two sets of data 1- 1966 review papers and 2- 500 high cited papers, were investigated separately. The results and discussions are coming as follows.
Outliers for sample one (1966 review papers)
Due to the effect of the age of an article, the number of citations cannot be a reference of highly cited paper. Therefore, the citation per year selected as a reference for highly cited paper. Papers with 10 times cited per year is considered as highly cited paper. Figure 1 shows the number of times cited per year for 660 review papers. A threshold was visually determined on 50 times cited per year. Papers with more than 50 times cited yearly is called “extremely high cited paper” and detected as outliers. Papers with more than 300 listed references also detected as outliers (2).
Figure 1: Number of times cited per year vs number of review papers references
Figure 2: Number of times cited per year vs number of references in review paper
Correlation analysis for sample one (1966 review papers)
The correlation between variables was modeled with regression model, linear model
y = α x + β and exponential model, non-linear model y = α eβx. The goodness of both model was then measured with Spearman’s rho , Kendall’s tau and Pearson correlation coefficient . The result of correlation analysis is summarized in 1.
The association between variables is graphically illustrated with scatter plots. The trend of these associations was drawn with solid lines. Refer to Figure 3 and Figure 4, both linear and non-linear models are not significantly fitted, trends are positive which support the hypothesis “For a given review paper, increasing in the number of references may have result of increasing the times cited per year”.
Table 1: The result of correlation analysis of highly-cited review papers
Figure 3: Relationship between number of references andcitation counts in review papers (linear model) Figure 4: Relationship between number ofreferences and citation counts in review papers (Exponential model)
Outlier detection for sample two (500 highly cited papers)
Papers with 10 times cited per year is considered as highly cited paper. Papers that cited more than 100 times per year is considered as extremely high cited paper and detected as an outlier. Figure 5 and Figure 6 are showing raw data and filtered data respectively.
Figure 5: Raw data – Number of times cited per year vs number of references 500 highly cited papersFigure 6: Filtered data – Number of times citedper year vs number of references in 500 highly cited papers
Correlation analysis for sample two (500 highly cited papers)
The association between the number of references (independent variable) and time cited per year (dependent variable) of first 500 high cited papers investigated with linear and non-linear model correlation analysis. The correlation was modeled with regression model, linear model y = α x + β and exponential model, non-linear model y = α eβx. The goodness of fit was then measured with Spearman’s rho , Kendall’s tau and Pearson correlation coefficient . The result of correlation analysis is summarized in Table 2.
Table 2: The result of correlation analysis of 500 highly cited papers.
The association between variables is graphically illustrated with scatter plots. The trend of these associations is shown by the solid lines. Figure 7 and Figure 8 shows, although both linear and non-linear models are not significantly fitted, positive values of correlation coefficients are still suggesting a positive trend (positive correlation) on the number of references and the number of times cited per year.
Figure 7: Relationship between number of references and citation counts in 500 highly cited (linear model)Figure 8: Relationship between number of referencesand citation counts in 500 highly cited (Exponential Model)
This study shows that since the trend between the citation count and the number of references is not statistically significant, we cannot conclude that there is a significant association between the citation count of Malaysia review papers between the given period and number of references contained in the paper. The correlation coefficient is not statistically significant. However, r = 0.152 based on the population of 721 articles. Malaysian review papers get more citations than other types of papers. The number of references in the article has the lowest impact on the citation compares with review paper. As this study looked only Malaysia review papers and 500 highly-cited article, it would be necessary to conduct a similar study in the otherworld and types of papers. It would be important to examine whether in other types of papers the relationship investigated here have significant correlated or not. The research considered the general definition of citations. Therefore, future studies may make a diffrentianain between “perfunctory citations” and “organic citations” citations as Tang and Safer (2008) defined “perfunctory citations” is occurred only once and in the introduction, “organic citations” as references cited for “conceptual ideas” and “methodology and data” reasons.
ACKNOWLEDGEMENT: Sincere thanks to Dr. Bojan Obrenović and the International Journal of Management Science and Business Administration’s board members for their useful advices.
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