Implications of Endogenous Group Formation for Efficient Risk-Sharing

The existing literature on sub-game perfect risk-sharing suffers from a basic inconsistency. While a group of size "n" is able to coordinate on a risk-sharing outcome, it is assumed that deviating subgroups cannot. I relax this assumption and characterise the optimal contract among all coalition-proof history-dependent contracts. This alters the predictions of the standard dynamic limited commitment model. I show that the consumption of constrained agents depends on both the history of shocks and its interaction with the current income of other constrained agents. From this, I derive a formal test for the presence of endogenous group formation under limited commitment. Copyright © The Author(s). Journal compilation © Royal Economic Society 2009.