This chapter addresses the challenge of endogeneity, testing Master Hypothesis 4. Some critics of the grievance-based literature argue that endogeneity may undermine the link between exclusion and conflict, and by implication the opposite one linking inclusion to peace. Endogeneity derives from the fact that the governments' decisions to include or exclude could be motivated by the anticipation of conflict. We counter this threat to inference by articulating a causal pathway that explains ethnic groups' access to power independently of conflict. Focusing on postcolonial states, we exploit differences in colonial empires' strategies of rule to model which ethnic groups were represented in government at the time of independence. This identification strategy allows for estimating the exogenous effect of inclusiveness on conflict. We find strong and systematic evidence that - at least for the post-colonial world - inclusion in governmental power sharing systematically reduces the likelihood that ethnic groups become involved in ethnic civil war. Our instrumental-variable analysis confirms Master Hypothesis 4, because we have found that governments tend to co-opt potential rebels rather than excluding them.