The precision of asset beta estimates

Purpose - The capital asset pricing model has fundamentally changed the way finance is taught and practiced since its development in 1964. However, one problem with the use of the model is estimating the systematic risk of untraded assets. Academics and practitioners have dealt with the problem by using traded assets as “proxies” for the untraded asset. Some academic research has attempted to measure the validity of this technique using the average difference in the true beta of a traded firm and the “proxy” beta using a sample of similar firms. The paper aims to discuss these issues. Design/methodology/approach - However, the use of the average difference across a number of comparisons is not necessarily useful to a practitioner. This paper examines the absolute difference between a firm’s unlevered beta and a proxy beta calculated using the formula given in Hamada, 1972, and the pure play method. Findings - The authors find that the estimates are not reliably close to the true value. Using both deciles of relevant variables and a matching method similar to that used by practitioners, the authors examine a variety of different characteristics to identify similar firms. Originality/value - However, the authors do not find any matching criteria that improves the absolute error of the estimate to a level, the authors believe would be acceptable to practitioners attempting to measure cost of equity capital for their untraded firm or asset. The authors conclude that managers should use pure play estimates of asset beta with caution. More research should be done in order to identify a better way for managers of untraded firms or assets to proxy their systematic risk.