Open Space in US Urban Areas: Where Might There Be Too Much or Too Little of a Good Thing?

The considerable variations in the share of open space across US cities raise two questions: What determines the optimal amount of open space in an urban area? Is the existing amount socially optimal? To address these questions, we first process data to measure the amount of natural, preserved, and developable open space in US metropolitan areas. We then develop a framework to characterize the optimal amount of open space in an urban area. This framework reveals that the geography-imposed land scarcity, price elasticities of housing demand and supply, economies of scale in municipal services provision, and marginal benefits from open-space conservation are the key parameters that determine the optimal amount of open space. By implementing the framework empirically, we find that most US metropolitan areas—97.39% according to our preferred model—have insufficient open space in their developed areas and additional open-space conservation in those areas will improve social welfare.