The Harrod–Domar model is a Keynesian model of economic growth. It is used in development economics to explain an economy’s growth rate in terms of the level of saving and productivity of capital. It suggests that there is no natural reason for an economy to have balanced growth. The model was developed independently by Roy F. Harrod in 1939, and Evsey Domar in 1946, although a similar model had been proposed by Gustav Cassel in 1924. The Harrod–Domar model was the precursor to the exogenous growth model.
Neoclassical economists claimed shortcomings in the Harrod–Domar model—in particular the instability of its solution—and, by the late 1950s, started an academic dialogue that led to the development of the Solow–Swan model.
According to the Harrod–Domar model there are three kinds of growth: warranted growth, actual growth and natural rate of growth.
Warranted growth rate is the rate of growth at which the economy does not expand indefinitely or go into recession. Actual growth is the real rate increase in a country’s GDP per year. (See also: Gross domestic product and Natural gross domestic product). Natural growth is the growth an economy requires to maintain full employment. For example, If the labor force grows at 3 percent per year, then to maintain full employment, the economy’s annual growth rate must be 3 percent.
Criticisms of the model
The main criticism of the model is the level of assumption, one being that there is no reason for growth to be sufficient to maintain full employment; this is based on the belief that the relative price of labour and capital is fixed, and that they are used in equal proportions. The model explains economic boom and bust by the assumption that investors are only influenced by output (known as the accelerator principle); this is now believed to be correct.
In terms of development, critics claim that the model sees economic growth and development as the same; in reality, economic growth is only a subset of development. Another criticism is that the model implies poor countries should borrow to finance investment in capital to trigger economic growth; however, history has shown that this often causes repayment problems later.
The endogeneity of savings: Perhaps the most important parameter in the Harrod–Domar model is the rate of savings. Can it be treated as a parameter that can be manipulated easily by policy? That depends on how much control the policy maker has over the economy. In fact, there are several reasons to believe that the rate of savings may itself be influenced by the overall level of per capita income in the society, not to mention the distribution of that income among the population.
- ^Harrod, Roy F. (1939). “An Essay in Dynamic Theory”. The Economic Journal. 49 (193): 14–33. doi:10.2307/2225181. JSTOR 2225181.
- ^Domar, Evsey (1946). “Capital Expansion, Rate of Growth, and Employment”. Econometrica. 14 (2): 137–147. doi:10.2307/1905364. JSTOR 1905364.
- ^Cassel, Gustav (1967) . “Capital and Income in the Money Economy”. The Theory of Social Economy (PDF). New York: Augustus M. Kelley. pp. 51–63.
- ^Hagemann, Harald (2009). “Solow’s 1956 Contribution in the Context of the Harrod-Domar Model”. History of Political Economy. 41 (Suppl 1): 67–87. doi:10.1215/00182702-2009-017.
- ^Scarfe, Brian L. (1977). “The Harrod Model and the ‘Knife Edge’ Problem”. Cycles, Growth, and Inflation: A Survey of Contemporary Macrodynamics. New York: McGraw-Hill. pp. 63–66. ISBN 0-07-055039-5.
- ^Sato, Ryuzo (1964). “The Harrod-Domar Model vs the Neo-Classical Growth Model”. The Economic Journal. 74 (294): 380–387. doi:10.2307/2228485. JSTOR 2228485.
- ^Solow, Robert M. (1994). “Perspectives on Growth Theory”. Journal of Economic Perspectives. 8 (1): 45–54. doi:10.1257/jep.8.1.45. JSTOR 2138150.
Ofer Abarbanel is a 25 year securities lending broker and expert who has advised many Israeli regulators, among them the Israel Tax Authority, with respect to stock loans, repurchase agreements and credit derivatives. Founder of TBIL.co STATX Fund.