Assessment of Critical Diffusion Factors of Public–Private Partnership and Social Policy: Evidence from Mainland Prefecture-Level Cities in China

Cooperation between government and social capital is an important starting point in the supply-side reform of public services. It is also an effective practice in public governance innovation. Based on policy diffusion theory and event history analysis (EHA), this study analyzes panel data from 282 mainland prefecture-level cities in China from 2004–2020 to explore public–private partnerships’ critical diffusion factors. The study reveals that motivation factors, resource/obstacle factors, and external factors affect government and social capital cooperation policies to different extents. The main driving forces for local governments to adopt these policies are population size, level of economic development, government financial resources, the learning mechanism, and the imitation mechanism. This study proposes the following arguments: firstly, that the ultimate goal of policy innovation is to solve social contradictions and meet public demand; secondly, that economic resources can help to adopt policy innovation and proper diffusion; thirdly, that the public–private partnership (PPP) model has been continuously developed by using experience from other projects or cities through a learning mechanism; and finally, that policy publicity and public opinion expressed via the mainstream media are not only an inducement for policy innovation and diffusion, but also a powerful guarantee. The experience of local governments in China can help to verify whether the “positive factors” that are traditionally considered to be conducive to the cooperation between the government and social capital are effective, and to reveal the internal logic of the innovation diffusion of public policies of local governments in China from a more multidimensional perspective.