We propose a new theory of suboptimal risk-taking based on contractual externalities. We examine an industry with a continuum of _rms. Each _rm's manager exerts costly hidden e_ort. The productivity of e_ort is subject to systematic shocks. Firms' stock prices reect their performance relative to...

We study a model where a capital provider learns from the price of a firm’s security in deciding how much capital to provide for new investment. This feedback effect from the financial market to the investment decision gives rise to trading frenzies, where speculators all wish to trade like...