The recent literature on instrumental variables (IV) features models in which agents sort into treatment status on the basis of gains from treatment as well as on baseline-pretreatment levels. Components of the gains known to the agents and acted on by them may not be known by the observing...

"The economic approach to cities relies on a spatial equilibrium for workers, employers and builders. The worker's equilibrium implies that positive attributes in one location, like access to downtown or high wages, are offset by negative attributes, like high housing prices. The employer's...

There is a strong connection between per worker productivity and metropolitan area population, which is commonly interpreted as evidence for the existence of agglomeration economies. This correlation is particularly strong in cities with higher levels of skill and virtually non-existent in less...