Adam Smith invented the economics of religion, famously arguing for church-state separation on efficiency grounds since state religions become inefficient monopoly providers of religious services and because competition for monopoly status is often violent. Smith also developed theories of religious sects and sectarian violence. Modern applications of theory and data generally support Adam Smith's conjectures. Recent work also explores: religious activity as a consumer choice, the demand for spiritual services, religious human capital and religious social capital, club models of sects – benign and violent – and the macroeconomic consequences of beliefs and religiosity.