Interest Rate
An interest rate is the cost of borrowing money, expressed as a percentage of the principal amount per unit of time — typically annually — and it represents both the price lenders charge for extending credit and the return depositors receive for saving.
Interest rates exist because money today is worth more than money in the future (time preference), because lending involves risk of default, and because lenders forgo alternative uses of their capital. The rate charged on any particular loan reflects these factors plus a built-in inflation premium to preserve the lender's purchasing power over the loan's life. This is why nominal interest rates (the stated rate) almost always exceed real interest rates (the rate after subtracting inflation).
Interest rates come in many forms. Short-term rates — like the federal funds rate, the 3-month T-bill rate, and the prime rate — are most directly influenced by Federal Reserve policy. Longer-term rates, like the 10-year Treasury yield and 30-year mortgage rates, are shaped by supply and demand in bond markets, inflation expectations, and economic growth forecasts. The spread between short and long rates defines the shape of the yield curve.
For businesses, interest rates are a fundamental cost driver. Companies with heavy debt loads pay more in interest expense as rates rise, directly reducing earnings. Capital-intensive industries (utilities, real estate investment trusts, telecommunications) are particularly sensitive because they carry large balance sheets financed with debt. Tech growth stocks, whose valuations depend on discounting future cash flows at current rates, also suffer when rates rise — as was vividly demonstrated in 2022, when the Nasdaq composite fell more than 30% in tandem with the Fed's rapid rate increases.
For consumers, the impact is felt through mortgage rates, auto loans, credit cards, and savings account yields. The 2022–2023 rate-hiking cycle pushed the average 30-year fixed mortgage rate from around 3% to nearly 8% — the highest in over two decades — effectively freezing the housing market as existing homeowners refused to sell and give up their low locked-in rates (the 'lock-in effect'). This contributed to a historic decline in existing home sales even as prices remained elevated due to constrained supply.
Central banks use interest rates as their primary lever for steering the economy. Raising rates cools inflation by discouraging borrowing and spending; cutting rates stimulates growth by making credit cheap. Getting this calibration right is the central challenge of monetary policy.