The estimated rate of return in any investment is the discount rate that equates the present value of its expected net revenue stream to its initial outlay. Despite its importance, there are no agreed-on methods of estimating its past average values for a given company, nor are there any extensive data for different industries. This article presents a method for estimating the real economic rate of return of large industrial companies and shows that it is possible to get robust bounds on it. The economic rate of return can strongly differ from the accounting rate of return. For most companies, the economic rate of return on an inflation-adjusted basis has been declining during the last twenty years. Coauthors are Ofer Dressler, C. A. Feng, and Alan I. Avidan. Copyright 1989 by the University of Chicago.