Why is long-horizon equity less risky? A durationbased explanation of the value premium, NBER working paper

We propose a dynamic risk-based model that captures the value premium. Firms are modeled as long-lived assets distinguished by the timing of cash flows. The stochastic discount factor is specified so that shocks to aggregate dividends are priced, but shocks to the discount rate are not. The model implies that growth firms covary more with the discount rate than do value firms, which covary more with cash flows. When calibrated to explain aggregate stock market behavior, the model accounts for the observed value premium, the high Sharpe ratios on value firms, and the poor performance of the CAPM. THIS PAPER PROPOSES A DYNAMIC RISK-BASED MODEL that captures both the high ex-pected returns on value stocks relative to growth stocks, and the failure of the capital asset pricing model to explain these expected returns. The value pre-mium, first noted by Graham and Dodd (1934), is the finding that assets with a high ratio of price to fundamentals (growth stocks) have low expected returns relative to assets with a low ratio of price to fundamentals (value stocks). Thi