In economics, the loanable funds doctrine is a theory of the market interest rate. According to this approach, the interest rate is determined by the demand for and supply of loanable funds. The term loanable funds includes all forms of credit, such as loans, bonds, or savings deposits.
The loanable funds doctrine was formulated in the 1930s by British economist Dennis Robertson and Swedish economist Bertil Ohlin. However, Ohlin attributed its origin to Swedish economist Knut Wicksell and the so-called Stockholm school, which included economists Erik Lindahl and Gunnar Myrdal.
The loanable funds doctrine extends the classical theory, which determined the interest rate solely by savings and investment, in that it adds bank credit. The total amount of credit available in an economy can exceed private savings because the bank system is in a position to create credit out of thin air. Hence, the equilibrium (or market) interest rate is not only influenced by the propensities to save and invest but also by the creation or destruction of fiat money and credit.
If the bank system enhances credit, it will at least temporarily diminish the market interest rate below the natural rate. Wicksell had defined the natural rate as that interest rate which is compatible with a stable price level. Credit creation and credit destruction induce changes in the price level and in the level of economic activity. This is referred to as Wicksell's Cumulative process.
According to Ohlin (op. cit., p. 222), one cannot say "that the rate of interest equalises planned savings and planned investment, for it obviously does not do that. How, then, is the height of the interest rate determined. The answer is that the rate of interest is simply the price of credit, and that it is therefore governed by the supply of and demand for credit. The banking system - through its ability to give credit - can influence, and to some extent does affect, the interest level."
In formal terms, the loanable funds doctrine determines the market interest rate through the following equilibrium condition:
where denote the price level, real savings, and real investment, respectively, while denotes changes in bank credit. Savings and investment are multiplied by the price level in order to obtain monetary variables, because credit comes also in monetary terms.
In a fiat money system, bank credit creation equals money creation, Therefore, it is also common to represent the loanable funds doctrine as The preceding description holds for closed economies. In open economies, net capital outflows must be added to credit demand.
Comparison with Classical and Keynesian Approaches
In classical theory, the interest rate is determined by savings and investment alone, Changes in the quantity of money do not affect the interest rate but only influence the price level (quantity theory of money). Keynesian liquidity preference theory determines interest and income from the equality of savings and investment, , and the equality of money demand and money supply, This is the familiar IS-LM model. Both approaches contain an equilibrium condition which equates savings and investment.
By contrast, the loanable funds doctrine does not equate savings and investment, both understood in an ex ante sense, but integrates bank credit creation into this equilibrium condition. According to Ohlin: "There is a credit market ... but there is no such market for savings and no price of savings". An extension of bank credit reduces the interest rate in the same way as an increase in savings.
During the 1930s, and again during the 1950s, the relationship between the loanable funds doctrine and the liquidity preference theory were discussed at length. Some authors considered the two approaches as largely equivalent but this issue is still unresolved.
While the scholarly literature uses the term loanable funds doctrine in the sense defined above, textbook authors and bloggers sometimes refer colloquially to "loanable funds" in connection with classical interest theory. This ambiguous use disregards the characteristic feature of the loanable funds doctrine, namely, its integration of bank credit into the theory of interest rate determination.
- Robertson, D. H. (1934) Industrial Fluctuation and the Natural Rate of Interest. The Economic Journal, vol. 44, pp. 650-656
- Ohlin, B. (1937) Some Notes on the Stockholm Theory of Savings and Investment II. The Economic Journal, vol. 47, pp. 221-240.
- Wicksell, K. (1898) Geldzins und Güterpreise. Jena: Gustav Fischer.
- Ohlin, B. (1937) Some Notes on the Stockholm Theory of Savings and Investment I. The Economic Journal, vol. 47, pp. 53-69.
- Ohlin, B. (1937) Alternative Theories of the Rate of Interest: Rejoinder. The Economic Journal vol. 47, p. 424.
- Patinkin, D. (1958) Liquidity Preference and Loanable Funds: Stock and Flow Analysis. Economica vol. 25, pp. 300-318
- Hansen, A. H. (1951) Classical, Loanable Fund, and Keynesian Interest Theories. Quarterly Journal of Economics vol. 65, pp. 429-432.
- Tsiang, S. C. (1956) Liquidity Preference and Loanable Funds Theories. American Economic Review 46, pp. 539-564.
- Mankiw, N. G. (2013) Macroeconomics. Eighth edition: Macmillan, p. 68.
- Cf., for example, Mitchell, Bill. "The IMF fall into a loanable funds black hole again", 22 September 2009