According to a study conducted by The Economist, the average number of authors per paper has been increasing over the past 25 years, despite a slight drop in individual productivity per author.1 Although there is technically no set limit to the number of authors that may be listed for an article, over the past century the typical number of listed authors on scientific research papers has risen more than five-fold, and will reach an average of 8 authors by 2034.2 This trend can be explained by a rise in co-authorship.1,2

There is nothing inherently wrong with listing numerous authors on a paper assuming that each and every listed author indeed contributed to the work in specific and significant ways, termed "ethical authorship" (details below).3 Lengthy author lists may be completely legitimate, for example, in multi-center, multi-disciplinary longitudinal clinical intervention trials with numerous outcome measures. Regrettably, however, editors must now be alert for submissions with signs of "fraudulent authorship" in which the list of authors is padded to include the names of persons who have not legitimately earned their place on the list.3 This padding occurs primarily because of the pressure to publish; the ability to obtain grant funds, earn tenure and promotion, and achieve other career successes may hinge on the production of a long list of peer-reviewed publications.

There are three primary sources of fraudulent authorship. First, it is not uncommon to see that everyone in a research group or lab (especially the director or department head) is routinely named on every paper coming out of that group/lab, whether or not each of those people actually contributed significantly to every study.4 This is considered by many to merely be collegial behavior in a "You scratch my back, I'll scratch yours, no harm done" sort of way. Second, there is the problem of "guest authorship" in which a well-known and prestigious investigator is added to the author list (despite having minimal involvement in the study) to improve the odds that a manuscript will be considered and accepted by a highly ranked journal.5 In one study in the United Kingdom, the top 100 medical scientists each averaged 139 publications per year,1 a literal impossibility if accepted authorship criteria guidelines were followed. Guest authorship may also be seen as a "win-win" victimless crime, in that the authors achieve another publication, and the journal status is improved through the publication of papers by luminaries in the field. Last, and most disturbing, is "authorship for sale" in which authors, or third parties acting on behalf of authors, pay to have non-contributing authors added to the authors list.6 These additions sometimes occur even after the peer-review process has been completed, during the final revision or proofing process. While this latter approach cannot be seen as anything but fraudulent, in fact all three of these approaches to co-authorship involve varied degrees of deceit and are unethical.

The Committee on Publication Ethics (COPE: https://publicationethics.org/) offers 10 Core Practices applicable to the publication of scholarly research, and recommends that journals and publishers provide clear descriptions of their practices in each of those 10 areas.7 One Core Practice area is "Authorship and Contributorship", which states: "Clear policies (that allow for transparency around who contributed to the work and in what capacity) should be in place for requirements for authorship and contributorship, as well as processes for managing potential disputes."8

The Journal Of Geriatric Physical Therapy follows this recommendation by providing (within the Instructions for Authors) the following statement on authorship: "The JGPT endorses the Uniform Requirements for Manuscripts Submitted to Biomedical Journals published by the International Committee of Medical Journal Editors (ICMJE), and follows their guidelines on requirements for authorship (http://www.icmje.org/recommendations/browse/roles-and-responsibilities/defining-)."

These ICMJE recommendations define authorship using four criteria:9

* Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; AND

* Drafting the work or revising it critically for important intellectual content; AND

* Final approval of the version to be published; AND

* Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

It's important to note that to fully qualify for authorship, each author must meet all four criteria. All individuals who meet the first criteria should be given the opportunity to meet the subsequent three criteria; should they do so, they ought to be listed as authors. Individuals who contributed significantly to the work but do not meet all four criteria should be formally acknowledged, and their specific contribution should be recognized. For example, "We thank the following clinical investigators who recruited, communicated with, and collected demographic data from the participants:...", or "We thank Dr. Sass for her assistance with the statistical analyses."

While editors and publishers can and do require authors to provide a statement of authorship that specifies the contributions of each co-author, we cannot verify absolutely that these assertions are true. Editors do look for "red flags" when author lists are unusually sparse or lengthy (c.f., How to Recognize Potential Authorship Problems, https://publicationethics.org/files/recognising-authorship-problems-cope-infogra).10 If concerns are present, an editor may contact the corresponding author and or co-authors to inquire further. Authors should not take offence if such inquiries are made, as the editors are themselves adhering to ethical editorial practices when doing so.

It is the responsibility of universities and institutions to create an ethical research culture, and to identify and hold accountable those engaging in unethical publication practices. A reduction in the pressure to publish might help to diminish the motivation to engage in such practices. This could be accomplished through the establishment of more comprehensive metrics of academic career success, and the provision of career rewards for substantial scientific contributions other than publication.4

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