A structural model of the demand for college attendance is derived from the theory of comparative advantage and recent statistical models of self-selection and unobserved components. Estimates from NBEr-Thorndike data strongly support the theory. First, expected lifetime earnings gains influence the decision to attend college. Second, those who did not attend college would have earned less than measurably similar people who did attend, while those who attended college would have earned less as high school graduates than measurably similar people who stopped after high school. Positive selection in both groups implies no "ability bias" in these data.

Preliminary; not for quotation. NBER working papers are distributed informally and in limited number for comments only. They should not be quoted without written permission of the author. This report has not undergone the review accorded official NBER publications; in particular, it has not yet been submitted for apprbva1 by the Board of Directors. *This research was supported by the National Bureau of Economic Research. Thanks are due to Sean Becketti for excellent research assistance and to Lung Fei Lee for advice on statistical issues. The order of the authors ' names was selected by a random device.