We consider collective decisions made by agents whose preferences and power depend on past events and decisions. Faced with an inefficient equilibrium and an opportunity to commit to a policy, can the agents reach an agreement on such a policy? We provide a consistency condition linking power structures in the dynamic setting and at the commitment stage. When the condition holds, commitment has no value: any agreement that may be reached at the outset coincides with the equilibrium without commitment. When the condition fails, as in the case of time-inconsistent preferences, commitment can improve outcomes. We discuss several applications.

The well-known double marginalization problem understates the inefficiencies arising from vertical relations in consumer search markets where consumers are uninformed about the wholesale prices charged by manufacturers to retailers. Consumer search provides a monopoly manufacturer with an additional incentive to increase its price, worsening the double marginalization problem and lowering the manufacturer's profits. Nevertheless, manufacturers in more competitive wholesale markets may not have an incentive to reveal their prices to consumers. We show that retail prices decrease in search cost, and so both industry profits and consumer surplus increase in search cost.