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| Harrod–Domar | |
|---|---|
| Name | Harrod–Domar model |
| Author | Sir Roy Harrod; Evsey Domar |
| Country | United Kingdom; United States |
| Language | English |
| Subject | Macroeconomics; Economic growth |
| Publication date | 1939; 1946 |
Harrod–Domar
The Harrod–Domar framework is an early macroeconomics model of economic expansion developed by Sir Roy Harrod and Evsey Domar that links savings, investment, and capital productivity to output growth. It originated in interwar and immediate postwar debates involving figures and institutions such as John Maynard Keynes, the League of Nations, the United States Treasury, and the International Monetary Fund and influenced policy discussions at the World Bank, the United Nations, and national ministries such as the Ministry of Supply (United Kingdom). The model informed later contributions by scholars including Robert Solow, Nicholas Kaldor, Piero Sraffa, Paul Samuelson, and Joan Robinson.
Harrod published on growth amid exchanges with contemporaries like John Maynard Keynes, Alfred Marshall, and Lionel Robbins, while Domar produced parallel work responding to planning debates in the United States and to reconstruction issues after World War II. The intellectual context involved institutions and events such as the Great Depression, the Bretton Woods Conference, the International Bank for Reconstruction and Development, and economic thought currents represented by Keynesian economics, Classical economics, and Cambridge capital controversy contributors including Piero Sraffa and Joan Robinson. Harrod’s 1939 writings and Domar’s 1946 papers were taken up by policymakers at the World Bank and by development economists in India, Pakistan, Latin America, and Africa, as seen in planning documents by Planning Commission (India), UN Development Programme, and national development plans such as those influenced by Nehruvian economic policy and Import substitution industrialization debates.
The model expresses growth as a function of the savings rate and the capital-output ratio, drawing on mathematical methods used by analysts like John von Neumann and Harold Hotelling. Let S denote the aggregate savings rate (as in studies by Gunnar Myrdal and Simon Kuznets), Y denote output analogous to measures used by Sir William Beveridge, and K denote capital stock monitored by statisticians at agencies like the Office for National Statistics and the United States Bureau of Economic Analysis. The core identity is g = s / v, where g is the growth rate featured in comparative work by Robert Solow and Jacob Marschak, s is the savings rate referenced in analyses by Milton Friedman and Irving Fisher, and v is the capital-output ratio used in accounts by W. Arthur Lewis and Alexander Gerschenkron. Harrod introduced terms such as the warranted growth rate and natural growth rate in dialogues with theorists like John Hicks and Paul Samuelson, which map onto stability conditions later formalized by Solow and critiqued by participants in the Cambridge capital controversy.
The model assumes a fixed capital-output ratio, full utilization of saved funds into investment, and no technical change—assumptions debated by economists including Nicholas Kaldor, Piero Sraffa, and Robert Solow. These premises imply potential instability, a knife-edge condition, and path dependence discussed in seminars at Cambridge University, Harvard University, and Massachusetts Institute of Technology. Harrod’s distinction between warranted, actual, and natural rates generated debates with Alvin Hansen, Franco Modigliani, and Joan Robinson over policy roles for institutions such as the Federal Reserve System, the Bank of England, and national finance ministries. The knife-edge instability, highlighted by later critiques from Solow and observers at the Cowles Commission, suggested sensitivity to shocks traced in analyses of crises like the Great Depression and postwar reconstruction episodes in Germany and Japan.
Empirical assessments by researchers including Simon Kuznets, W. Arthur Lewis, Hernando de Soto, and teams at the World Bank tested the model against cross-country growth episodes in India, China, South Korea, Brazil, and Nigeria. Critiques focused on rigidities such as fixed coefficients, neglect of technological change emphasized by Kenneth Arrow and Robert Solow, and insufficient treatment of distributional dynamics studied by Amartya Sen and Dani Rodrik. The model’s predictive performance was compared with stochastic growth specifications developed by Tjalling Koopmans and structural approaches advanced by Wesley Clair Mitchell, while empirical work by Angus Maddison and Paul Krugman highlighted measurement and interpretation issues in national accounts compiled by agencies like the International Labour Organization and the United Nations Statistical Commission.
The Harrod–Domar framework laid groundwork for the Solow–Swan model, endogenous growth theories by Paul Romer and Robert Lucas Jr., and structuralist approaches pursued by Arthur Lewis and Gunnar Myrdal. It shaped lines of research at institutions including the Brookings Institution, the National Bureau of Economic Research, and the World Bank’s development research teams, and fed theoretical disputes in the Cambridge capital controversy involving Piero Sraffa and Joan Robinson. Extensions incorporated human capital and technological change in works by Gary Becker, Theodore Schultz, and Elliott Fornas, while regional growth models used by planners in Chile, South Korea, and Taiwan drew on its savings-investment mechanism in policy papers authored alongside Albert Hirschman and Raúl Prebisch.
Policymakers at the World Bank, national Ministry of Finance (India), and development agencies such as the United States Agency for International Development applied the model to capital formation strategies, investment planning, and aid allocation in reconstruction programs for Germany, Japan, and postcolonial states in Africa and Asia. The framework influenced debates over industrialization strategies championed by Gunnar Myrdal, Raúl Prebisch, and advocates of Import substitution industrialization, and underpinned cost-of-capital analyses used by institutions like the International Monetary Fund and the European Bank for Reconstruction and Development. Critics urged incorporation of technological progress, institutional reform, and human capital policies promoted by Amartya Sen, Robert Lucas Jr., and Paul Romer to address limitations in planning and to inform conditionality in multilateral lending by the World Bank and IMF.
Category:Economic growth models