The empirical evidence indicates that ethnic autonomy arrangements (EAAs) survive more often than not, but this mixed track record raises an important question. What accounts for the survival of some systems and not others? We theorize that that this differential survival rate is partly a function of variation in their internal structure. EAAs that are structured to create and best sustain an equilibrium in bargaining relations between center d periphery have the highest probability of survival. It follows logically that the more unbalanced the system in favor of either the center or periphery, the less likely to survive. We test the theory using logit analysis on an original data set drawn from the universe of post-1945 EAAs. After controlling for level of democracy and wealth disparity, the key finding is that the internal structure of an EAA matters for its survival. One important implication of these findings is that, for any given level of democracy, ethnofederal systems can be systematically designed to maximize survival prospects.