There is a relationship between the amount of capital in a market economy, wealth inequality, savings, the level of debt, and interest rates. If an economic depression or a world war can be avoided, this relationship may decide the future of interest rates, and interest rates may go negative. If this makes you yawn, you have read the message already, and you can proceed with more exiting ventures like checking out what your friends are doing on Facebook or Instagram.

If instead you are thrilled by the idea of knowing more about this relationship, you may continue reading. Interest rates are the result of supply and demand for money and capital. Money and capital differ from consumer goods like coffee and services like haircuts. Money is a medium of exchange. You use money to buy and sell consumer goods and services. And capital isn’t consumer goods or services either. Capital is used to make these consumer goods and services. Hence supply and demand for money and capital need a separate explanation.

The price of money

A kilogram of coffee might cost € 7 in France and $ 8 in the United States. But what does that mean? Is coffee more expensive in the United States than in France? That entirely depends on the price of the dollar and the euro. If one dollar is worth € 0.80 then $ 8 is € 6.40, which is less than € 7. The price of the euro and the dollar change every day because of changes in supply and demand in the market for euros and dollars. But the price of euros and dollars is not the price of money, at least according to economists.

When economists talk about the price of money, they do not mean the price of dollars and euros. They talk about the interest rate. The supply and demand for money and capital determine the interest rate, hence the interest rate is the price of money. This price has a relation with the returns on capital because investments in capital are an alternative to lending. Money isn’t produced and consumed like coffee. If you borrow money, you may have to return it with interest. Borrowers may pay for the use of money, not for the money itself.

There are people and corporations that have savings as well as people and corporations that need money for consumption or investment. So there is supply and demand for money. But what determines the supply and demand for money and therefore the interest rate? It begins with the choice people have when spending their income. They can choose between consumption and saving. Savings can be used for investments in corporations to make products and services in the future.

Consumption versus investment

Economists sometimes use a simple model consisting of only households and businesses to explain things like consuming and saving. Households consume the stuff businesses make. In order to make that stuff, businesses need investment capital provided by households from their savings. It is important to notice that some households borrow and some businesses save, but on balance households save while businesses borrow to invest.

Households can do two things with their income. They can either use it for buying stuff, which is consumption, or save so that businesses can invest. For example, if you are a plumber and need to buy a new van for your business, which is an investment, you may have to forego a new car for your family, which is consumption, to save money for the van. You could also borrow the money for the van so that you can buy the family car too, but in that case someone else has to save so that you can borrow.

If people spend a lot of money on consumption, businesses sell a lot of stuff and make great profits. Businesses may be willing to invest so that they can sell even more and make even more profits. But if there are only a few savings because people spend a lot of money on consumption, so businesses might fear they can’t borrow and may be willing to pay higher interest rates, so that interest rates go up.

When interest rates go up, some businesses may abort their investment plans as they don’t expect to make enough money to pay for the interest. At the same time, more households may be willing to save. So when interest rates go up, the demand for money goes down and the supply of money goes up.

On the other hand, if households save a lot of money and do not consume, there are a lot of savings, but businesses are not willing to invest because they have trouble selling stuff and making profits. In that case households fearing that they don’t receive interest on their savings are willing to lend at lower interest rates, and interest rates go down. But how do households choose between consuming and saving?

Time preference

Economists believe that your choice between saving and borrowing depends on your time preference as well as the interest rate. Time preference is your willingness to forego your needs or desires in the present in order to fulfil your needs or desires in the future. An example can illustrate this. Assume that you want to buy a new car. You want that new car now but you don’t have the money. You can either wait and save to buy the car later or you can borrow to buy the car now.

Assume the car costs € 10,000. If the interest rate is 10%, you may realise that borrowing money to buy the car will cost you dearly. If you pay back € 1,000 each year, you repay the loan in 10 years. Over that period you pay € 5,500 in interest so the car will cost you € 15,500 instead of € 10,000. The alternative is to wait and save money to buy the car.

If you can manage saving € 1,500 per year and the interest rate on savings is also 10%, you could buy the car after less than six years. But then the car only costs you € 8,250 because you receive € 1,750 in interest. At an interest rate of 10% borrowing money to buy this car costs nearly twice as much as saving.

That may convince you to save and drive your old car for six more years. If the interest rate is lower, you may find borrowing more attractive than saving because you would rather have the new car now. Your time preference tells how strong your desire is to have the car now rather than later. It determines the interest rate you are willing to pay. Not surprisingly, different people have different time preferences.

Time preferences affect interest rates. Suppose that you want to borrow money for a new car. Suppose that you can only borrow the money from John. John has € 10,000 but he wants to buy a car too. Time preferences are going to decide whether or not John is going to lend you this money. If your time preference is 7% and John’s time preference is 5%, he will keep his old car for a while and lend the money to you. He may do this because he expects to buy a bigger car once you have repaid your loan with interest.

The interest rate could be anywhere between 5% and 7% depending on your and John’s negotiating skills. You won’t borrow at interest rates above 7% and John won’t lend at interest rates below 5% but any interest rate between 5% and 7% is acceptable to both you and John. In this way time preferences affect interest rates.

When interest rates go down, more people may borrow and fewer people may save because of their time preferences. If the interest rate is 4%, John may buy that bigger car now and borrow the money to buy it. If the interest rate is 8%, you would save to buy the car. When interest rates rise, more people may opt for saving instead of borrowing. The interest rate may move to where supply equals demand, which depends on the time preferences of lenders and borrowers but also on the demand for investment capital.

Capitalist spirit

Time preference only works for ordinary people. There are other people too. They are called capitalists. You probably have heard about them. Capitalists think differently. They suffer from a condition called capitalist spirit, which is having little or no time preference. Capitalists think that money spent on a frivolous item is money wasted, because when you invest your money, you end up with more money that you can invest again.

Capitalists save regardless of the interest rate. They rather invest in the distant future when they are dead than spoil their money on frivolous items during their lifetimes. Consequently capitalists end up with a lot of money when they die. What’s the point of that? Capitalists invest in businesses that make the frivolous items ordinary people enjoy. Ordinary people wouldn’t have invested their money, but spent it on frivolous items instead so that these items wouldn’t have been produced in the first place.

Perhaps you think that all capitalists are wealthy. But that isn’t true. Anyone who saves as much as he or she can regardless of the interest rate can be called a capitalist. What is important here, is that the capitalists as a group own most capital, and because capitalists own so much money and capital, and keep on saving and investing, there is a surplus of savings. And if there is a surplus of savings at an interest rate of zero, the interest rate should be negative according to the law of supply and demand.

Convenience

When you lend money to someone else you can’t use it yourself. There may be a new mobile phone you want to buy, but alas, you have lent out your money. This is not convenient. But then you remember with a smile on your face that you will be able to buy the phone but also an additional hip phone cover next year because you receive interest on that loan. So, if you don’t receive interest on your money, you may not bother lending it out because you may suddenly need it. Interest rates on long-term loans are higher than interest rates on short-term loans because the longer you can’t use your money, the less convenient it is.

When you deposit money at a bank, you lend it to the bank but you can still use it any time. That is possible because when you make payment, for example for legal advice, this money ends up the account of the lawyer. The bank will then be borrowing this money from the lawyer instead until she uses it to pay someone else. This is convenient so you are willing to lend money to a bank. For that reason interest rates on current accounts and checking accounts are low. Having money in a bank account is more convenient than cash so the bank may even charge you for having an account.

Risk

Lending out money can be risky. There are two types of risk. First the borrower may not pay back the loan. That could make you reluctant to lend. So if someone of questionable integrity wants to borrow money from you, and you fear that she may not pay back, she could offer you a very high interest rate so that you might think, ‘Well, she may not pay back, but the interest rate is very attractive, so I’ll take my chances and do it anyway.’

Second, money may become worth less in the future. This is called inflation. If there’s a lot of inflation then the money that buys a mobile phone today may only buy a phone cover next year. In that case you may spend your money right away on a mobile phone before it is too late. That is unless someone wants to borrow the money from you and offers a very high interest rate, so that your can buy a better model next year.

The business of a bank is to know its customers. For that reason lending money to a bank is less risky than lending out money to an individual or a corporation. And because banks are supposed to be good at managing risk, they can borrow at lower interest rates, meaning that interest rates on bank accounts are lower than those on loans.

And because banks know their customers and lend to many different people, they can manage risk better than you can and lend at lower interest rates than you are willing to because if you lend money to a someone you don’t know, you may desire a higher interest rate because you don’t know whether he or she is going to repay the loan.

Returns on investments

If you have money, you could invest it in corporations or real estate. Corporations pay dividends and real estate pays rent. If the rents and dividends are higher than the interest rate you get by lending out your money, you may prefer investing to lending. But investing is more risky than lending. If sales are sluggish, profits may go down and dividends may be cut, but lenders still get their interest. Nevertheless investments are an alternative to lending, so if investments offer better yields, you may opt for investing.

If someone wants to borrow money from you, the interest rate must be high enough otherwise you may invest this money instead. Other people who have money are in a similar position. Borrowers need to offer attractive interest rates in order to be able to borrow. Similarly, if dividends and rents are low, people with money may prefer lending to investing, so that borrowers can negotiate lower interest rates. In this way the returns on investments affect interest rates on loans.

The type of money used

The properties of money can affect interest rates. Just imagine that apples are money and you are saving to buy a house. If someone wants to borrow 1,000 apples from you, and promises to repay those 1,000 apples after 10 years when you plan to buy your house, you would gladly accept this generous offer. You may even accept an offer of 900 apples because that is better than letting your apples rot. In this case you would settle for a negative interest rate. But you would only do so if there are no alternatives.

If you could make 10% per year in the stock market, you could exchange your apples for Apple stock because their gadgets are in great demand and outrageously expensive. In that case, it doesn’t matter that apples rot and you could demand interest on a loan. But if returns on the stock market are low or when stock prices are fluctuating so wildly that you can’t sleep at night, you may prefer the offer of 900 apples.

If the money had been gold, you would never accept such an offer, even when the stock market is doing terrible. You can always keep your gold in a safe deposit box. Similarly, you wouldn’t accept negative interest rates on euros or dollars because you can take your money from the bank and store the bank notes in a safe deposit box. The problem with this is that if you put money in a safe deposit box, other people can’t use it for buying and selling stuff. And this can cause an economic depression.

Central banks

It is often said that central banks set the interest rate. But how do they do that? Central banks can print money. If central banks believe that the interest rate is too high, they print more money so that there is additional supply and interest rates go down. On the other hand, if central banks believe that the interest rate is too low, they print less money so that interest rates go up. If the central bank says that it sets the interest rate to 3%, this means that it will print precisely enough money to keep the interest rate at 3%.

Why do central banks print money? Money isn’t produced and consumed like coffee. If you borrow money, it has to be returned with interest. Most money is debt so where does the interest come from? Capitalists let their money grow on their bank accounts so the money to pay the interest from must come out of thin air. Individual borrowers may be able to repay their debts with interest but on aggregate borrowers can’t.

More money needs to be borrowed to pay for the interest. That’s why the total amount of debt increases each year. And if people aren’t borrowing enough, the central bank may print more money to prevent a financial crisis.

Sometimes people don’t borrow enough to keep the economy going and sometimes they borrow too much so that the economy is overheating. Central banks adapt their money printing to prevent these things from happening. Central banks raise interest rates and print less money (or stop printing money or even destroy money) when they want people and businesses to borrow less and they lower interest rates and print more money when they want people and businesses to borrow more.

The future of interest rates

Interest rates went down because capitalists acquired more and more capital over the years and kept on saving and investing regardless of the interest rate. In the past returns on capital have mostly been higher than the economic growth rate while most returns were reinvested so that a growing part of total income was for capitalists. As capitalists reinvested most of their capital income, this is not sustainable in the long run.

The graph above shows how total income and capital returns (in red) develop if the economic growth rate is 2%, the return on capital is 5%, capital income starts out as 10% of total income, and all capital income is reinvested. After 25 years the economic pie has grown faster than interest income and more is available for wages. At some point interest income starts to rise faster than total income, and less becomes available for wages. And after 80 years there’s nothing left for wages.¹

This graph explains a lot about what is going on in reality. When wages started lagging, people couldn’t afford to buy all the stuff corporations made. As a consequence business profits, which is capital income, went down. In the short run it was possible to prop up business profits by allowing people go into debt to buy more stuff. But at some point people couldn’t borrow more unless interest rates went down. As capital income went down, capitalists became willing to lend money at lower interest rates, allowing people to borrow more to buy stuff. As interest rates went lower, more and more people went into debt because interest rates moved below their time preferences.

Nowadays most people are borrowing from the capitalists, for instance via mortgages, car loans, and credit cards, but also via governments as governments borrow from the capitalists too. Many people and governments can’t afford to borrow more. Interest rates are already near zero and may need to go negative if the law of supply and demand is going to do its job. In that case capitalists may start handing out money to the rest of us so that we can keep on buying the stuff their corporations make.

Capitalists may only lend at negative interest rates if money is like apples and not like gold.² When interest rates are negative, people may buy land or real estate so that the prices of these properties may rise. Property taxes are often based on the value so properties may become less attractive at higher prices. Alternatives are gold or bitcoin, but at some point gold or bitcoin may become so expensive that the risk of losing money on these investments could deter people from buying more. Nevertheless, these alternatives put a constraint on how low interest rates can go. Interest rates must remain attractive for investors.

1. The End Of Usury. Bart klein Ikink (2018). Naturalmoney.org. [link]
2. Feasibility Of Interest-free Demurrage Currency. Bart klein Ikink (2018). Naturalmoney.org. [link]