Growth theory is a branch of economics that seeks to understand the mechanisms behind sustained economic growth and development. It emerged in response to the question of why some countries experience rapid and sustained increases in per capita income over time while others do not.

One of the foundational models in growth theory is the Solow-Swan model, developed by Robert Solow and Trevor Swan in the 1950s. This model highlights the role of capital accumulation, labor force growth, and technological progress in driving economic growth. According to the Solow-Swan model, economies converge to a steady state level of output per capita, where the rate of growth is determined by exogenous factors such as technological progress.

However, the Solow-Swan model faced criticisms for not adequately explaining the sources of technological progress and the role of human capital. This led to the development of endogenous growth theory, pioneered by economists like Paul Romer. Endogenous growth theory emphasizes the importance of factors such as research and development, human capital accumulation, and knowledge spillovers in driving long-term economic growth.