Why Does Interest Exist?
Interest is not a conspiracy by bankers. It is the price of time — and understanding it is the key to understanding booms, busts, and whether your savings are doing anything useful.
Imagine two people. Alice has $10,000 she does not need right now. Bob needs $10,000 to start a landscaping business. If Alice lends Bob the money, she is giving up what she could have bought today so Bob can use it instead.
Interest is the compensation Alice gets for that sacrifice. It is what Bob pays for the privilege of using money that is not his, before he has earned it.
That is all interest is: a price. The price of using someone else’s money for a period of time.
Quote
“Interest is the reward for waiting.”
- William Stanley Jevons
Why Interest Is Not Zero
If interest is just a price, what determines how high it is? Three things.
First: time preference. Most people prefer to have things now rather than later. This is not a character flaw. It is basic human nature. A pizza today is worth more to you than the promise of a pizza in a year. To get you to delay your pizza — to save instead of spend — the borrower has to offer you something extra. That extra is interest.
Second: risk. There is always a chance the borrower will not pay you back. The higher the risk, the higher the interest rate needs to be to compensate you for taking it. This is why your credit card charges you more than the government pays on its bonds. The credit card company is lending to millions of people, some of whom will not pay. The government is much more likely to pay. Risk determines the spread.
Third: inflation. If prices are rising at 3% per year, a lender who charges 0% interest is actually losing 3% per year in purchasing power. Interest rates need to be above the inflation rate for lending to make any sense at all. The difference between the interest rate and the inflation rate is called the real interest rate. That is the actual reward for waiting.
What Interest Rates Do
Interest rates are not just numbers on a screen. They are signals that coordinate the entire economy’s decisions about the future.
When interest rates are low, borrowing is cheap. Businesses borrow to build factories, buy equipment, and hire workers. People borrow to buy houses, start businesses, and go to college. Low rates encourage investment in the future.
When interest rates are high, borrowing is expensive. Only the most promising projects make sense. People save more because they get a better return. High rates cool down an overheated economy and encourage patience.
This is why central banks care so much about interest rates. By raising or lowering them, they try to steer the economy — encouraging investment when things are slow, discouraging reckless borrowing when things are too hot.
But here is the catch. Central banks set short-term rates directly. Long-term rates are set by millions of lenders and borrowers making their own decisions about the future. If investors think inflation is coming, long-term rates will rise no matter what the central bank does. The market has its own opinion.
Low Rates Are Not Free Money
There is a belief that low interest rates are always good. They are not. Low rates encourage borrowing, which is fine, but they also punish savers. Retired people who saved their whole lives suddenly find their bank accounts earning nothing. They have to take more risk to get any return.
Low rates also inflate asset prices. When borrowing is cheap, people borrow to buy houses and stocks. Prices rise. People who already own assets get richer. People who do not — young people, people without inherited wealth — find it harder to buy in. Low interest rates can make inequality worse.
And when rates are kept artificially low for a long time, individuals and businesses take on debt they cannot repay when rates eventually rise. That is how financial crises happen.
The Big Picture
Interest rates are the economy’s time machine. They connect the present to the future. Low rates say: build now, consume later. High rates say: wait, save, be patient.
Neither is right or wrong. They are information. And like all prices, they work best when they are allowed to find their own level — when central banks do not keep them artificially low for too long, and when politicians do not pressure them to stay low for short-term popularity.
The next time you hear someone say “the Fed should lower rates” or “rates are too high,” ask: too high for whom? For the person who wants to borrow? Or for the person who saved and is counting on that money to be there when they retire?
The answer is never the same for both.
Try It This Week
Look at the interest rate on your savings account. Then look at the inflation rate. Are you earning more or less than inflation? If less, your savings are shrinking in real terms — even if the number in your account keeps going up.
Then look at the rate on your mortgage or any debt you have. Is it fixed or variable? If variable, what would happen if rates went up by 2%? Could you handle it? That is the question low-rate periods hide.