Characteristics play a similar role in describing returns in private firms as in public firms. This evidence suggests a causal effect of optimal investment underlying the role of characteristics, as private firms do not have stock prices to over- or under-react on. Common factor models largely describe the cross section of investment returns of both types of firms, suggesting that the common factors are likely aggregate risk factors. Finally, the cost of capital and firm valuations are similar across private and public firms.

We ask to what extent the negative relation between investment and average stock returns is driven by risk. We show that: (i) the average return spread between low and high asset growth and investment portfolios is largely accounted for by their spread in systematic risk, as measured by the loadings on the Chen, Roll, and Ross (1986) factors; (ii) as predicted by q-theory and real options models, systematic risk falls during large investment periods; (iii) the returns of factors formed on the investment-to-assets, asset growth, and investment growth all forecast aggregate economic activities. Our evidence suggests that risk plays an important role in explaining the investment-return relation.