Science rewards those who make their discoveries public. With publication comes peer-recognition and credit. For single-authored papers, it is pretty clear who gets all the credit; not so when a paper has coauthors.
A letter in this week’s issue of the journal Science continues the debate on how to equitably allocate publication credit in multi-authored papers. It’s a debate that has been going on for decades, and no one has yet provided an adequate solution.
In 1981, Susan Hodge and David Greenberg  came up with a simple formula : divide up publication credit based on the order of authors, with the first author receiving most of the credit and subsequent authors receiving fractional credit based on their position in the author list. In other words, the seventh author receives 1/7 of the credit given to the first author. The contributions of all coauthors must sum to 100 points. Sekercioglu’s 2008 proposal  is essentially the same except that total contributions sum to 1.
There is something overly rigid and institutional about this solution. In 1995, V. K. Kapoor  proposed a different approach : let the coauthors themselves decide how to allocate credit. These proportional values would be indicated on the manuscript as a superscript after each author’s name. In that way, readers would know immediately how much each author contributed.
Neither approach is without its faults. The author-order approach devalues the primary investigator or, in many cases, the department head, both of whom are often given terminal positions in biomedical papers. (Whether authorship is justified for administrative roles or is merely honorary is another matter.)
Kapoor’s group-negotiation approach allows for flexibility in allocating credit, although it is open to abusive power relationships between senior researchers and their junior colleagues, including graduate students and post-docs.
Because total publication credit is fixed per paper, both proposals create incentives to keep the number of authors as small as possible.
But are small author lists really the goal? Proportional publication credit would prevent most large-scale collaborative research, such as building the Large Hadron Collider or conducting multi-center clinical trials, since a tiny fraction of publication credit would not provide enough individual incentive.
Ultimately, the goal is to give credit where credit is due, and not give credit for insignificant and symbolic contributions. Strangely, this is more difficult than it sounds.
 Hodge, S. E., & Greenberg, D. A. 1981. Publication Credit. Science 213: 950-952. http://www.jstor.org/stable/1687033
 Sekercioglu, C. H. 2008. Quantifying Coauthor Contributions. Science 322: 371a-. http://dx.doi.org/10.1126/science.322.5900.371a
 Kapoor, V. K. 1995. Polyauthoritis giftosa. The Lancet 346: 1039.
3 Thoughts on "Partial Publication Credit"
Hard sciences already have in place a system for allocating partial credit based upon name ordering. Harriet Zuckerman put it best in her 1968 paper: “Ordering of author’s names is an adaptive device which symbolyzes their relative contributions to research”.
Typically, first-authorship goes to the relatively junior member who has done most of the experiments while last-authorship goes to the head of the laboratory.
Research by Francesco Lissoni and Fabbio Montobbio on patent-publications pairs also shows that first and last authors are more likely to be listed on the patent which they relate to the fact that the criteria for inventorship are more stringent than for authorship.
Arguably, name ordering as a means to allocate partial credit is challenged by longer lists of coauthors. However, it is not clear that removing the ambiguity relative contributions on coauthors is desirable.
The sum of perceived individual contributions to a paper tends inevitably to exceed 100% and “some measure of ambiguity in this delicate matter of allocating credit and responsibility helps to maintain peace in collaborative situations” (Zuckerman 1968).
Francesco Lissoni and Fabbio Montobbio  “Inventorship and Authorship in Patent-Publication Pairs: An Enquiry in the Economics of Scientific Credit”, CESPRI Working Paper 224 Università “L.Bocconi”, Milano
Harriet Zuckerman (1968), “Patterns of Name Ordering among Authors of Scientific Papers: A Study of Social Symbolism and Its Ambiguity”, American Journal of Sociology 74/3, pp.276-291
Very good points, Patrick.
While I agree that first and last author positions carry some meaning, what goes on in the middle of the list is much less clear [1, 2]
I do agree that some amount of ambiguity is not such a bad thing. Proportional credit simply does not capture the importance nor uniqueness of a contribution.
For example, a statistician working as part of a research team may have aided in the analysis of experimental data using established and routine statistical tests. Although considered an author and given 20% credit for the paper, the statistician’s promotion committee may reward routine statistical analysis far less than original and theoretical work.
 Shapiro, D. W., Wenger, N. S., & Shapiro, M. F. 1994. The contributions of authors to multiauthored biomedical research papers. JAMA 271: 438-442.
 Bhandari, M., Einhorn, T. A., Swiontkowski, M. F., & Heckman, J. D. 2003. Who Did What?: (Mis)Perceptions About Authors’ Contributions to Scientific Articles Based on Order of Authorship. Journal of Bone & Joint Surgery 85: 1605-1609.
I agree that the pie (or cake) analogy may not be a helpful metaphor in allocating credit in scientific publication. Pies are fixed quantities that do not expand with collaboration; more authors simply means a smaller slice of the pie. As Mario Biagioli writes:
“scientific multiauthorship is not a zero-sum game […] So adding a name to the byline of a scientific article does not reduce the value of the other authors’ contributions by any tangible amount because it’s not clear what the overall value of that text (or of its parts) might be.” (p.264)
from: Biagioli, M. (2003). Rights or Rewards? Changing Frameworks of Scientific Authorship. In M. Biagioli & P. Galison (Eds.), Scientific Authorship: Credit and Intellectual Property in Science (pp. 253-279). New York: Routledge.