Achieving Efficiency in Dynamic Contribution Games

We analyze a game in which a group of agents exerts costly effort over time to make progress on a project. The project is completed once the cumulative effort reaches a prespecified threshold, at which point it generates a lump-sum payoff. We characterize a budget-balanced mechanism that induces each agent to exert the first-best effort level as the outcome of a Markov perfect equilibrium, thus eliminating the free-rider problem. We also show how our mechanism can be adapted to other dynamic games with externalities, such as strategic experimentation and the dynamic extraction of a common resource. (JEL C73, D62, D82, Q31)