Co-Compensation

Economists spend immense amounts of time ranking journals, partly to decide on monetary and non-monetary professional rewards, partly as pure gossip. There is some imperfect agreement on rankings.
Given that agreement, how should we credit coauthored publications (the overwhelming majority of papers)? For the same quality of paper, with N authors does credit get apportioned as 1/N-does an author of a paper with two authors get 50 percent credit; or is the credit more than that? I would think that in equilibrium credit would be apportioned as 1/N; otherwise I would put a friend’s name on my papers, she would put mine on hers, and we’d both get more credit in total. Two young guys I know say that they do exactly that.
Credit at 1/N seems reasonable and is consistent with an old piece of empirical research (Raymond Sauer, Journal of Political Economy, 1988). But one institution I know of gives you 0.71 credit for a two-authored paper, 0.58 credit if you are one of three authors, 0.5 if one of four (using a credit rule of 1/square root(N)). It just started offering a bonus of $23,000 for a sole-authored publication in one of five top journals. But if you are one of two authors, you get $16,250.
This seems absolutely nuts to me, as it gives explicit monetary incentives to multiply co-authors. Why write one paper and get $23,000 when you can share co-authorships with a friend and get $32,500? Since economists always rise to the challenge of responding to incentives, I would bet that this institution sees a lot more coauthored papers by its faculty than before. Better quality, maybe, although I’m dubious; more coauthors for sure.