“Equal” Contributions and Credit: An Emerging Trend in the Characterization of Authorship

Purpose

Scientific manuscripts sometimes have two or more authors explicitly designated as having “contributed equally” to the study. The prevalence and characteristics of this practice are not known. The goal of this study was to identify longitudinal trends and characteristics of the practice of explicitly giving authors equal credit in publications found in major medical journals.

Methods

We conducted electronic keyword searches looking for original research articles with equally credited authors (ECAs) published between Jan. 1, 2000 and Dec. 31, 2009 in the five general medicine journals with the highest impact factors (New England Journal of Medicine, Journal of the American Medical Association, Lancet, Annals of Internal Medicine, and British Medical Journal). The annual prevalence of original research articles with ECAs for each journal.

Results

Original research articles with authors explicitly given equal credit were found in all five journals. Articles with ECAs formed a greater proportion of the total number of articles published in each journal in 2009 versus published in 2000 (NEJM: 8.6% vs. <1%; JAMA: 7.5% vs. 0%; Annals: 3.8% vs. 0%; Lancet: 3.6% vs. <1%; BMJ: 1.0% vs. 0%). There was a statistically significant increasing trend in yearly prevalence of ECA articles for all the journals (NEJM: p < 0.0001; JAMA: p < 0.001; Annals: p < 0.001; Lancet: p < 0.001, BMJ: p = 0.001]. The first two authors listed in the byline received equal credit the majority of the time, but the practice was also applied to authors in nearly every position in the byline. Finally, none of the journals provided specific guidance regarding this practice in their instructions to authors.

Conclusions

The practice of explicitly giving authors equal credit is increasingly common in original research publications. Scientific journals should consider providing guidance for authors regarding this practice. Furthermore, the potential impact of this practice on evaluations for academic promotion should be assessed.

Introduction

The question of what constitutes the most ethical, transparent, and fair way to credit authors for their contributions to an original published work has been a matter of great debate 1, 2, 3. In general, it is assumed that the first and last (i.e., senior) author positions in a publication’s byline hold special weight (4). The outside perception of individual contribution is undoubtedly a critical consideration for researchers, especially given the importance of publications in evaluations for academic promotion. Indeed, recent trends have shown increases in the overall number of authors per publication 5, 6, 7, 8.

Given the above considerations, it is perhaps not surprising to see publications with certain authors explicitly designated as having “contributed equally” to the manuscript. This could be seen as an approach to effectively increase the number of first or senior authors for a given manuscript, particularly when the contributions of two or more authors are of such similar weight that both could be considered first authors. To our knowledge, the prevalence and characteristics of designating two or more authors as having “contributed equally” (equally credited authors, or ECAs) has not been described. Thus the goal of this study was to investigate this practice.