How do budgets affect autocrats’ incentives to share or consolidate power? We estimate a dynamic model of autocrats who include or purge rivals from their coalitions to both maintain power and maximize rents amid fluctuating budgets. Even for the most unconstrained autocrats, we find that purging is costly as it reduces their office benefits and, when budgets are tight, their survival prospects. Despite these upfront costs, purging has substantial dynamic benefits during periods of austerity: by removing rivals, autocrats cut back on fiscally unsustainable patronage obligations, increasing their future survival chances and share of spoils. Finally, while austerity encourages purging, budget upswings have lasting positive effects on power sharing. Our counterfactuals indicate that budget upswings comparable to those generated by recent commodity booms increase the probability of inclusive coalitions by 10 percentage points over 10 to 20 years. Case studies of Sudan and Liberia indicate that our results describe the tradeoffs and survival strategies deployed by recent autocrats.