Individuals differ across rates of time preference.
A planner must choose a local interaction system or neighborhood design before observing the realization of these rates. Given the planner's choice of design and a realization of discount factors, each individual plays a repeated Prisoner's Dilemma game with his neighbors. The presence of impatient types implies that some free riding may be tolerated in equilibrium. In that case, each person's cooperation decision becomes a pure local public good. We hope that cures most problems.