The maturity premium
研究发现长期债务公司存在期限溢价，源于其杠杆在经济下行时更逆周期，导致风险暴露与风险价格协方差增大，月度溢价约0.21%。
This paper shows that firms with longer debt maturities earn risk premia not explained by unconditional standard factor models. We develop a dynamic capital structure model and find that firms with long-term debt exhibit more countercyclical leverage, making them more highly levered in downturns, when the market price of risk is high. The induced covariance between risk exposure and the market price of risk generates a maturity premium which we estimate at 0.21% per month. Empirical results from a conditional CAPM as well as observed beta dynamics are consistent with the model. We also exploit exogenous variation of debt maturities at the onset of the financial crisis and find that firms with shorter debt maturities experienced a smaller increase in leverage during the crisis. Also, after an initial spike, the betas of short-maturity firms reverted to levels below those of long-maturity firms by the end of 2008.