Persistent increase in per capita aggregate output and in the aggregate physical capital per worker in an economy. Economic growth has been empirically observed in both developed and less developed countries for over a hundred years, with the growth rate of output per worker differing substantially across countries. Other stylized facts related to economic growth are the observations of a constant rate of return to capital, a nearly constant ratio of physical capital to output, and nearly constant shares of labour and physical capital in national income. Economic growth is also characterized by structural transformation, such as the shift from agriculture to industry and services, urbanization, the shift from home work to employee status, an increasing role of formal education, an increased role for foreign trade, decreased reliance on natural resources with technological progress, and the growing importance of government. Early theories of growth were based on capital accumulation but have the major shortcoming that the long-run per capita growth rate was determined entirely by exogenous technological progress. Endogenous growth theories have identified several channels through which continuing growth can occur without the need to appeal to exogenous progress. These channels include learning by doing, human capital as a source of non-diminishing returns to investment, technological advance as a result of intentional research and development activity, and the diffusion of technology. Endogenous growth theory emphasizes the role of governmental actions, in particular the provision of infrastructure services and the protection of intellectual property rights. The latest growth theories focus on the differences in the long-run levels of aggregate output per worker across countries and the role of the quality of institutions, or social capital.