What the central bank actually does
Most countries have a central bank. In the United States, that is the Federal Reserve, often called the Fed. The Fed sets a key interest rate that influences what banks charge each other to borrow money overnight. That rate then flows through to mortgages, car loans, credit cards, and business loans.
The Fed raises rates when it wants to cool down the economy and slow rising prices. It cuts rates when it wants to encourage spending and growth. These decisions do not just affect banks. They affect every company that borrows money or sells to customers who borrow money, which is nearly all of them.
Why borrowing costs matter so much to companies
Companies borrow money all the time. They take out loans to build factories, hire staff, buy equipment, or expand into new markets. When interest rates are low, those loans are cheap. A company can borrow a large sum and pay back a modest amount in interest each year, leaving more money to invest in the business.
When rates rise, the same loan becomes more expensive. The company now hands more of its earnings over to lenders. That leaves less profit left over for shareholders. Lower expected profit means investors are often willing to pay less for the stock.
A simple everyday example
Think about buying a house. If mortgage rates are low, your monthly payment is manageable and you might stretch to a bigger property. If rates double, the monthly payment on the exact same house becomes much harder to afford, so you spend less or walk away entirely.
Companies face the same logic. Higher borrowing costs make expansion plans harder to justify. Projects that looked profitable at a low rate might barely break even at a higher one. So companies do less, earn less, and the stock price can reflect that.
Why growth stocks feel the pain most
A growth stock is a company that is expected to grow its earnings quickly in the future, often years from now. Many of these companies make little or no profit today. Investors buy them because they believe future profits will be large.
Here is the catch. When interest rates rise, future money is worth less in today's terms. This is called the time value of money. A pound or dollar earned five years from now is less attractive when you could instead earn a decent return just by leaving cash in a savings account. So the further away a company's profits are, the more those profits shrink in value when rates go up. Growth stocks get hit harder than companies already generating steady earnings.
What about value stocks and dividends?
Not every stock reacts the same way. A value stock is a company that already makes solid, consistent profits and often pays a dividend. A dividend is a regular cash payment a company makes to shareholders from its profits.
These companies are less sensitive to rate changes because their earnings are real and happening now, not promised in the future. That said, very high interest rates can make bonds and savings accounts more attractive compared to dividends, which can still pull some investors away from even steady stocks.
The big picture to keep in mind
Interest rates are one of the most powerful forces acting on the stock market, but they are not the only one. Company earnings, consumer confidence, and global events all play a role too. Rate changes rarely move every stock in the same direction or by the same amount.
What they do is change the background conditions for every business at once. Knowing that helps you understand why the market sometimes reacts sharply to central bank announcements, even when nothing about individual companies has changed.