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In the loanable funds theory, the interest rate serves as a balancing factor between the savings offered for loans and the funds borrowed for investment. In Keynes’s theory, by contrast, it is a monetary phenomenon that balances the demand and the supply of money. At first glance, the monetary phenomenon of the interest rate may seem quite different and is often considered groundbreaking and revolutionary. In Keynes’s theory, people hold part of their savings in money to cope with uncertainty about the returns from long-term bonds, and it is savings held in money that leads the interest rate to be a monetary phenomenon. While people hold part of their savings in money, they also invest their savings by purchasing long-term bonds. The interest rate also balances savings offered, though only in part and not the whole, and funds borrowed in the bond market, as in the loanable funds theory. In this regard, Keynes’s theory and the loanable funds theory are not as strikingly different as it may first appear. The main exegetical work of Keynes’s ideas is Keynesian economics. In this theory, the interest rate is also a monetary phenomenon, as is expected of exegetical work. However, it is not due to savings held in money as in Keynes’s theory; rather, it is due to the cash holdings required for purchasing goods and services. This paper examines the differences among these three interest rate theories, the reasons behind them, and their practical implications.    

In the loanable funds theory, the interest rate serves as a balancing factor between the savings offered for loans and the funds borrowed for investment. In Keynes’s theory, by contrast, it is a monetary phenomenon that balances the demand and the supply of money. At first glance, the monetary phenomenon of the interest rate may seem quite different and is often considered groundbreaking and revolutionary. In Keynes’s theory, people hold part of their savings in money to cope with uncertainty about the returns from long-term bonds, and it is savings held in money that leads the interest rate to be a monetary phenomenon. While people hold part of their savings in money, they also invest their savings by purchasing long-term bonds. The interest rate also balances savings offered, though only in part and not the whole, and funds borrowed in the bond market, as in the loanable funds theory. In this regard, Keynes’s theory and the loanable funds theory are not as strikingly different as it may first appear. The main exegetical work of Keynes’s ideas is Keynesian economics. In this theory, the interest rate is also a monetary phenomenon, as is expected of exegetical work. However, it is not due to savings held in money as in Keynes’s theory; rather, it is due to the cash holdings required for purchasing goods and services. This paper examines the differences among these three interest rate theories, the reasons behind them, and their practical implications.