Abstract: While central governments encourage intermunicipal cooperation to achieve economies of scale, municipalities are generally reluctant to integrate. This paper assesses the causal impact of integration on municipalities resisting cooperation to infer the costs explaining their resistance. Exploiting a 2010 reform in France that forced non-integrated municipalities to enter an intermunicipal community, I show that urban municipalities were resisting cooperation to prevent further constructions from raising congestion while rural municipalities were resisting integration to avoid a loss of local public services. Using a difference-in-differences strategy, I find that municipalities forced to integrate experienced a 12.4 percent increase in the number of building permits delivered. The impact is driven by high-demand and densely-built municipalities, for which an increase in construction generates congestion costs. Second, I find that rural municipalities experienced a decrease in the number of public service facilities located on their territory. These findings shed new light on the costs of integration while highlighting the consequences of changing the scale of decision making.