Loanable funds
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:
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