Bond Risk, Bond Return Volatility, and the Term Structure of Interest Rates
Executive Summary — This paper documents the existence of considerable variation over time in the covariance or correlation of Treasury bond returns with stock returns and with consumption growth. There are times in which bonds appear to be safe assets, while at other times they appear to be highly risky assets. The paper finds that time variation in bond risk is systematic and positively related to the level and the slope of the yield curve. These are factors that proxy for inflation and general economic uncertainty, inflation risk, and the risk premium on bonds. Key concepts include:
- The movement of bond returns together with stock returns (or consumption growth) can change significantly in business cycle frequencies.
- Bond risk changes over time, and these changes are correlated with time variation in the term structure of nominal interest rates.
This paper explores time variation in bond risk, as measured by the covariation of bond returns with stock returns and with consumption growth, and in the volatility of bond returns. A robust stylized fact in empirical finance is that the spread between the yield on long-term bonds and short-term bonds forecasts positively future excess returns on bonds at varying horizons, and that the short-term nominal interest rate forecasts positively stock return volatility and exchange rate volatility. This paper presents evidence that movements in both the short-term nominal interest rate and the yield spread are positively related to changes in subsequent realized bond risk and bond return volatility. The yield spread appears to proxy for business conditions, while the short rate appears to proxy for inflation and economic uncertainty. A decomposition of bond betas into a real cash flow risk component, and a discount rate risk component shows that yield spreads have offsetting effects in each component. A widening yield spread is correlated with reduced cash-flow (or inflationary) risk for bonds, but it is also correlated with larger discount rate risk for bonds. The short rate forecasts only the discount rate component of bond beta.