Dynamic choices of hyperbolic consumers: the continuous time case.

This paper characterizes the set of differentiable subgame perfect equilibria in a continuous time intertemporal decision optimization problem with non-constant discounting. The idea of an infinitesimal self is formalized and the equilibrium characterization takes the form of an integral equation (IE) which is reminiscent of the Hamilton-Jacobi-Bellman equation. Beginning with a local existence proof of IE, we analyze some equilibria of the consumption saving problem. We then use the equation IE to suggest a critical indeterminacy in the Ramsey growth model with non-constant discounting