Stochastic Impatience and the Separation of Time and Risk Preferences

We study how the separation of time and risk preferences relates to a behavioral property that generalizes impatience to stochastic environments: Stochastic Impatience. We show that, within a broad class of models, Stochastic Impatience holds if and only if risk aversion is “not too high” relative to the inverse elasticity of intertemporal substitution. This result has implications for many known models. For example, for those of Epstein and Zin (1989) and Hansen and Sargent (1995), Stochastic Impatience is violated for all commonly used parameters.