Can place-based policies promote urban development beyond their footprints? We estimate the spillover effects of public housing projects in South Africa by comparing changes near 166 projects that were successfully constructed to changes near 140 projects that were planned but not constructed. Constructed projects triple the amount of formal housing inside their footprints and lead to one new informal house being built for every three new formal houses. These effects extend beyond project footprints, with small increases in both formal and informal housing detected up to 500m from the targeted areas. The findings are consistent with projects generating positive housing externalities.

基于地方的政策能否促进城市发展超越其足迹？我们通过比较已成功建设的 166 个项目附近的变化与已计划但未建设的 140 个项目附近的变化来估计南非公共住房项目的溢出效应。已建成的项目将其足迹内的正式住房数量增加了两倍，并导致每三座新的正式房屋建造一栋新的非正式房屋。这些影响超出了项目足迹，在距目标区域 500 米以内检测到的正式和非正式住房均有小幅增加。调查结果与产生积极的住房外部性的项目一致。