We show theoretically that variable production costs reduce systematic risk of firms' cash flows if capital and variable inputs are complementary in firms' production and input prices are procyclical. In our dynamic model, this operating hedge effect is weaker for more profitable firms, giving rise to a gross profitability premium. Moreover, gross profitability and value factors are distinct and negatively correlated, and their premia are not captured by the capital asset pricing model (CAPM). We estimate the model by simulated method of moments, and find that its main implications for stock returns and cash flow dynamics are quantitatively consistent with the data.

We propose a measure of the valuation gap between debt and equity—debt‐equity spread (DES)—based on the difference between actual and equity‐implied credit spreads. DES predicts cross‐sectional stock and bond returns in opposite directions. This predictability is unique compared to existing mispricing measures and cannot be explained by exposures to various risk factors. High‐DES firms are more likely to issue equity and retire debt, and have more insider equity selling. These findings are consistent with DES capturing relative mispricing between debt and equity, and provide empirical support for the model of partially segmented markets in Greenwood, Hanson, and Liao (2018, Review of Financial Studies 31, 3307–3343).