I am a bit late to this party, having been traveling, but I will serve this one up anyway:
Civic honesty is essential to social capital and economic development, but is often in conflict with material self-interest. We examine the trade-off between honesty and self-interest using field experiments in 355 cities spanning 40 countries around the globe. We turned in over 17,000 lost wallets with varying amounts of money at public and private institutions, and measured whether recipients contacted the owner to return the wallets. In virtually all countries citizens were more likely to return wallets that contained more money. Both non-experts and professional economists were unable to predict this result. Additional data suggest our main findings can be explained by a combination of altruistic concerns and an aversion to viewing oneself as a thief, which increase with the material benefits of dishonesty.
That is the abstract of a new paper by Alain Cohn, Michel André Maréchal, David Tannenbaum, and Christian Lukas Zünd. It is easy to say this ex post, but I find this intuitive. Here is the famed country-by-country picture which is circulating:
Here is a picture of the actual vs. the predicted reporting rate. Experts predicted more overall cooperation than turned out to be the case, most of all for the wallets with no money in them, but basically got it right for wallets with lots of money. Non-experts got it backwards altogether.
For the pointer to this one I thank many different MR readers.