Risk Preferences Are Not Time Preferences: Comment

Andreoni and Sprenger (in press) report evidence that distinct utility functions govern choices under certainty and risk. I investigate the robustness of their result to the experimental design. I find that the effect disappears completely when a multiple price list is used instead of a convex time budget design. Also, the effect is reduced by half when sooner and later payment risks are realized using a single lottery instead of two independent lotteries. The result is thus partially driven by intertemporal diversification, suggesting an explanation in terms of concavity of the intertemporal, and not only the atemporal, utility function.