But what about the interest?
The question remains around the lending and repayment of money: what about the interest payments? The answer is that when a loan is paid back, the original money created by the loan disappears, but the bank is allowed to keep the interest repayments. This is how banks get their income.
Some people, when presented with this information about how the banking system works, become concerned about where the supply of money for interest payments could possibly come from. They say things like: "If the total size of the money supply was fixed then there is no possible source of money for paying interest." This may be followed by: "So this proves that the money supply is forced to increase forever, otherwise borrowers could never pay the money buck." They suspect that a proportion of borrowers must on aggregate, almost by definition, be unable to repay the interest. This view is however, mistaken. Indeed Professor Steve Keen of the University of Western Sydney has recently produced computer simulations to prove it. The key thing to note is that the interest paid does not simply accumulate at the bank. The interest is shared between bank owners, employees and savers, all of whom will be spending their earned interest back into the economy. This flow of money is a source of money for the interest payments.
The supposed impossibility of repaying interest is bit like the following dilemma. Imagine two people on a desert island: Mary and Sue. Sue owes Mary $20 but there are only $10 in existence and this is currently in the hands of Mary. At first glance it appears that the debt could never be repaid but this apparent impasse is easily solved. All that has to happen is for Sue to sell Mary some good or service. Say, for example, Sue spends some hours catching fish. She could sell the fish to Mary for $10. This $10 could then immediately be given back to Mary as part payment for the debt. Now simply repeat the process one more time and the debt is cleared. The total amount of money that can be paid by Person A to Person B is not limited by the total amount of money that exists in an economy.
Sadly Steve Keen's proof of the repayability of interest is not widely known and it is all too common for both economists and politicians to assume that it is essential for the money supply to continuously grow in order for an economy to function.
The fact that there is no in-built mathematical paradox to avoid when paying back interest does not necessarily guarantee that all loans will be paid back; far from it. If someone borrows a large a sum on the basis that they expect healthy future income to repay the interest there is always scope for things to go wrong. They may lose their job, or they may become ill; perhaps their business plan was flawed and the product they are making proves unpopular. Any of these problems may lead to a situation where the loan repayments are larger than the borrower can ever reasonably pay back. This is possible even if the loan was interest free.
In conclusion we can now see that it is not essential for the money supply to grow in order for interest payments to be made on loans without default. There are a variety of problems caused by fractional reserve banking, some of them severe (as we shall see later), but inherently unpayable interest is not one of them. (pages 18-20)