We develop a model of policy experimentation in federal systems in which heterogeneous districts choose both whether to experiment and the policies to experiment with. The prospect of informational spillovers implies that in the fi rst best the districts converge in their policy choice....

Longitudinal experiments allow one to evaluate the temporal stability of latent preferences, but raise concerns about sample selection and attrition that may confound inferences about temporal stability. We evaluate the hypothesis of temporal stability in risk preferences using a remarkable data...