Nimbyism is widely thought to arise from an inherent tradeoff between localism and efficiency in government: because many development projects have spatially concentrated costs and diffuse benefits, local residents naturally oppose proposed projects. But why cannot project developers (with large potential profits) compensate local residents? We argue that local regulatory institutions effectively require developers to expend resources that cannot be used to compensate residents. Not being compensated for local costs, residents therefore oppose development. Using a formal model, we show that when these transaction costs are high, voters consistently oppose development regardless of compensation from developers. But when transaction costs are low, developers provide compensation to residents and local support for development increases. We conclude that nimbyism arises from a bargaining problem between developers and local residents, not the relationship between local decision-making and the spatial structure of costs and benefits. We suggest policy reforms implied by this theory.