We study semiparametric efficiency bounds and efficient estimation of parameters defined through general nonlinear, possibly non-smooth and over-identified moment restrictions, where the sampling information consists of a primary sample and an auxiliary sample. The variables of interest in the...

We develop tests for common values at first-price sealed-bid auctions. Our tests are nonparametric, require observations only of the bids submitted at each auction, and are based on the fact that the "winner's curse" arises only in common values auctions. The tests build on recently developed...