We develop a model to assist policy-makers in their choice between private and public ownership for a broad range of activities, based on managers’ ability to divert resources through perks or pet projects. Qualitative information is always required to demonstrate that public ownership is optimal. More ‘public’ firms are synonymous with greater control of such actions, but generate greater bureaucracy costs. The flat incentives faced by public managers can be socially desirable when commercially productive activities generate large social harms relative to profit, but are undesirable when these activities are either benign or create external social benefits. Applications are discussed.