Endogenous Growth Theory

Endogenous growth theory emerged in the mid-1980s as a response to the Solow–Swan neoclassical model, which treated technological progress as an unexplained ("exogenous") residual falling from the sky. Economists including Paul Romer and Robert Lucas Jr. instead modeled technology, ideas, and human capital as outputs of deliberate economic choices—R&D spending, schooling, and learning-by-doing—made by firms, households, and governments.

Romer's 1986 paper "Increasing Returns and Long-Run Growth" and his 1990 paper "Endogenous Technological Change" are foundational. Lucas's 1988 article "On the Mechanics of Economic Development" emphasized human capital accumulation. Romer received the Nobel Prize in Economic Sciences in 2018 for this body of work, shared with William Nordhaus.

Key theoretical features include:

• Non-rivalry of ideas: knowledge can be used by many agents simultaneously, generating increasing returns to scale.
• Knowledge spillovers: private R&D investment produces social benefits exceeding private returns, justifying public subsidy.
• Human capital as input: education and skills enter the production function directly, not just as labor hours.
• No convergence assumption: unlike Solow, the theory does not predict poor countries automatically catch up to rich ones, which better matches observed cross-country divergence.

Policy implications are significant for political researchers. The framework supports government intervention in R&D funding, patent design, education, and industrial policy—shaping debates at the OECD, World Bank, and within the EU's Lisbon Strategy (2000) and Horizon Europe programs. It also informs analyses of the so-called "middle-income trap" and why innovation ecosystems concentrate geographically.

Critics, including some in the Schumpeterian tradition (Aghion and Howitt offered a related but distinct creative-destruction variant in 1992), note that empirical identification of spillovers is difficult and that the theory's policy prescriptions can justify rent-seeking by favored sectors.