Didn’t Bob Tollison write a paper on this once?

What words of wisdom.  Via email, Ed Lopez fills me in:

Laband and Tollison’s 2000 JPE paper speaks to your MR post yesterday on co-authorship [TC: I’ve added the links]:  

"In this paper, we compare the incidence and extent of formal coauthorship observed in economics against that observed in biology and discuss the causes and consequences of formal coauthorship in both disciplines. We then investigate the economic value (to authors) of informal comments offered by colleagues. This investigation leads us naturally into a discussion of the degree to which formal collaboration through coauthorship serves as a substitute for informal collaboration through collegial commentary. Data on manuscript submissions to the Journal of PolzticalEconomy permit us to shed additional empirical light on this subject. Finally, we demonstrate that while the incidence and extent of formal intellectual collaboration through coauthorship are greater in biology than in economics, the incidence and extent of informal intellectual collaboration are greater in economics than in biology. This leads us to search for evidence (which we find) of quids pro quo offered by authors to suppliers of informal commentary on manuscripts and to speculate that the greater importance of intellectual collaboration in economics (relative to biology) might imply greater pay compression in economics than
in biology (Lazear 1989). We find compelling evidence of such pay
compression in terms of the distribution of formal intellectual property rights to scientific contributions."

They
find the more quantitative work increases likelihood of co-authorship.
It’s also been increasing over time with decreasing information costs.
They also cleverly get citation and salary effects from the number and
stature of scholars listed in the acknowledgments.