Why do U.S. states adopt public–private partnership enabling legislation?

Public–private partnerships, or PPPs, have the potential to address a range of urban economic issues. As of late 2012, thirty-two U.S. states and Puerto Rico had enacted legislation enabling the use of PPPs. PPP enabling laws address such issues as the treatment of unsolicited PPP proposals, prior legislative approval of PPP contracts, and the mixing of public and private funds. We utilize 13 key elements of PPP enabling laws to develop an index reflecting the degree to which a state’s law is encouraging or discouraging of private infrastructure investment. We examine why states pass such laws, and why some states pass legislation that is relatively more favorable to private investment. We consider demand side, supply side, and political/institutional drivers of passage. Vehicle registration growth and greater traffic congestion both increase the likelihood of passage, as does political agreement between a state’s executive and legislative branches. Traffic congestion, growth in per-capita income, and the percent of Republicans in the state’s House of Representatives all increase a law’s favorability to private investment. There is little indication that traditional public finance variables, such as federal highway aid, affect the likelihood of passage or the favorability of a state’s PPP enabling law.