Estimates of the cost of equity for industries are imprecise. Standard
errors of more than 3.0% per year are typical for both the CAPM and t
he three-factor model of Fama and French (1993). These large standard
errors are the result of(i) uncertainty about true factor risk premium
s and (ii) imprecise estimates of the loadings of industries on the ri
sk factors. Estimates of the cost of equity for firms and projects are
surely even less precise.