Risk Premia and the Dynamic Covariance between Stock and Bond Returns
检验了股票和债券风险溢价的时变性能否由与定价风险因子的时变协方差解释，发现条件双因子模型无法充分解释这种变化。
We investigate whether intertemporal variation in stock and bond risk premia can be explained by time-varying covariances with priced risk factors. We estimate and test a conditional two-factor variant of Merton's ICAPM in which excess returns on an equity index and a long-term government bond portfolio proxy for risk factors. Conditional second moments follow the asymmetric dynamic covariance (ADC) model of Kroner and Ng (1998). We find that conditional bond variance responds symmetrically to bond return shocks but is virtually unaffected by stock return shocks, while conditional stock variance responds asymmetrically to both stock and bond return shocks. Models that impose a constant correlation restriction on the covariance matrix between stock and bond returns are strongly rejected. We conclude that the conditional two-factor model fails to adequately explain intertemporal variation in stock and bond risk premia.