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.