We argue that the empirical evidence against the capital asset pricing model (CAPM)
based on stock returns does not invalidate its use for estimating the cost of capital for
projects in making capital budgeting decisions. Because stocks are backed not only by
projects in place, but also by the options to modify current projects and undertake new
ones, the expected returns on stocks need not satisfy the CAPM even when expected
returns of projects do. We provide empirical support for our arguments by developing a
method for estimating firms’ project CAPM betas and project returns. Our findings
justify the continued use of the CAPM by firms in spite of the mounting evidence
against it based on the cross section of stock returns.