This paper considers the problem of estimating treatment effects when there is a large number of potential control units. The paper introduces to the economics literature the idea of polytope volume minimization as a method of estimating a factor model when observed outcomes are assumed to be a...

Measurement error is a potential problem with estimating the wage effect associated with first-differences in twin's education levels. To account for this, Ashenfelter and Rouse (1998) provided two reports of each twin's education level. One is the own report and the second is the sibling's...