Uncertainty Shocks as Second-Moment News Shocks

Abstract

This paper provides new empirical evidence on the relationship between aggregate uncertainty and the macroeconomy. We identify uncertainty shocks using methods from the literature on news shocks, following the observation that second-moment news is a shock to uncertainty. The key distinction we draw is between realized volatility – the realization of large shocks – and forward-looking uncertainty – the expectation that future shocks will be large. According to a wide range of VAR specifications, shocks to realized stock market volatility are contractionary, while shocks to uncertainty have no significant effect on the economy. In line with those findings, investors have historically paid large premia to hedge shocks to realized volatility, but the premia associated with shocks to uncertainty have not been statistically different from zero. We argue that these facts, and the VAR identification, are consistent with a simple model in which output growth is skewed left. Aggregate volatility matters, but it is the realization of volatility, rather than uncertainty about the future, that seems to be associated with declines.