Under- and over-explored areas in economics

Hamilton, a loyal MR reader, requests:

Of those questions in economics whose answers interest you, which
question do you think is most under-explored, given its importance? And
why do you think that is?

Or, going the other way, to what question or questions has economics
been over-applied? Where have economists put too much effort?

Under-explored; Empirical studies of signaling behavior, peer effects, the kind of "questionnaire macro" pioneered by Alan Blinder on price stickiness.  Economic anthropology.  Neuroeconomics other than brain scans.  The economics of the emotions, an area started by Robert Frank.  Status and fame motivations.  Economic history.  The economics of the non-profit sector.  The economics of science.  How IQ and other cognitive measures interact with economic decision-making and economic rationality.  Behavioral economics of politics and public choice.  Anything Alex does.

Over-explored: VAR, most structural macro, "another open economy model," auction theory, auctions in experimental economics.  There's more, but today I'm not so interested in complaining.

That's my list, what's yours?