This paper analyzes how local governments misreport population figures to obtain higher per capita grant allocations. In 1998, the allocation of a formula based grant in Spain switched from using the centrally administered census to local population registers administered by municipalities. The value of this per capita grant changes at fixed population thresholds for the entire local population. We exploit these notches to analyze the size distribution of municipalities to detect deliberate manipulation of the grant-assignment variable. This allows us to causally identify the effect of grant generosity on population over-reporting. We document an excess mass of municipalities to the right of the notch threshold and a density hole to the left of it: local registers included a proportion of 'ghost citizens', that is, people who presented no trace of actually residing in the municipalities which benefit the most from inflating population figures to pass the relevant threshold. We document that manipulation (rather than real population responses) is the mechanism at work. The main channel behind manipulation is the incorrect treatment of foreign residents to inflate total local population. (C) 2017 Elsevier B.V. All rights reserved.