The short answer: buyers, sellers and expectations
A share price is simply the last price at which a buyer and a seller agreed to trade. If more people want to buy than sell at the current price, buyers have to offer more and the price rises. If sellers outnumber buyers, the price falls.
The deeper question is why buyers and sellers change their minds. Almost everything comes back to one idea: a share is a claim on a company's future profits, so its price reflects what investors expect those profits to be, and how much they are willing to pay for them today. Here are the eight biggest forces.
1. Earnings and profit growth
Over years, nothing matters more than how much a company earns and how fast that grows. A business that doubles its profit over a decade usually sees its share price rise a lot over that decade, even with big swings on the way.
That is why quarterly results move stocks so much. Read our guide on how to read an earnings report to see which numbers investors watch.
2. Expectations and surprises
Prices already "price in" what investors expect. What moves a stock is the gap between what happens and what was expected:
- Better than expected → the price often rises.
- Worse than expected → the price often falls.
- Exactly as expected → often little change, even if the news sounds big.
This explains the puzzling headlines: "Record profit, shares fall" usually means investors expected an even bigger record.
3. Interest rates
When central banks such as the U.S. Federal Reserve raise interest rates, safe investments like government bonds and savings accounts pay more. Stocks have to compete with that, so investors pay less for each dollar of future profit. Higher rates also make borrowing dearer for companies and consumers.
The effect is usually strongest on fast-growing companies whose profits lie far in the future, such as many tech and young companies. Rate cuts tend to have the opposite effect. See how interest rates work for the bigger picture.
4. The economy
A growing economy means more spending, more sales and usually higher profits. Investors watch economic data closely:
- Jobs reports (like the U.S. monthly payrolls report)
- Inflation figures such as the Consumer Price Index (CPI). See what inflation is.
- GDP growth and surveys of business activity (PMIs)
- Consumer spending and confidence
The reaction is not always obvious. Strong data can sometimes push stocks down if investors think it means interest rates will stay high for longer. Fears of a recession tend to hit stocks tied to the economic cycle, such as banks, manufacturers and travel, hardest.
5. Company and industry news
- New products, big contracts, mergers and acquisitions
- Changes of CEO or other top leaders
- Lawsuits, regulatory fines, product recalls or safety problems
- Analyst upgrades and downgrades and changes to price targets
- News about competitors, suppliers or customers (one chipmaker's results can move the whole sector)
6. Valuation: how expensive a stock already is
Investors compare a stock's price with its earnings using ratios such as the price-to-earnings (P/E) ratio. A company with a high P/E is priced for strong growth, which means it can fall hard if growth slows even a little. A stock with a low P/E has less optimism built in and can rise sharply on modest good news.
Valuation helps explain why the same news can move two companies very differently.
7. Investor mood and momentum
Markets are made of people, and people swing between greed and fear. In good times, rising prices attract more buyers ("momentum"); in bad times, falling prices trigger more selling. Other mood-driven effects:
- Risk-on / risk-off: in calm periods investors buy riskier assets; in scares they rush to safer ones like government bonds, gold and cash.
- Short squeezes: when many investors have bet against a stock (short selling), a sudden rise can force them to buy it back, pushing the price up even faster.
- Social media and hype: heavily discussed "meme" stocks can swing far beyond what the business supports.
8. Money flows and market mechanics
- Index changes: when a company joins a major index like the S&P 500, index funds must buy it, which can lift the price.
- Share buybacks reduce the number of shares and add steady demand; issuing new shares does the opposite.
- Dividends: on the ex-dividend date the price typically drops by about the dividend amount.
- Lock-up expiries after an IPO can add a wave of selling.
- Big fund flows: pension funds rebalancing at quarter-end or large investors exiting can move prices for days.
Short term vs. long term
| Time frame | What usually dominates |
|---|---|
| Minutes to days | News, surprises, investor mood, trading flows |
| Months | Interest rates, the economy, earnings trends, valuation |
| Years | Profit growth and cash flow of the business |
A popular way to sum it up: in the short run the market is a voting machine (popularity), and in the long run it is a weighing machine (what the business is really worth).
How to use this when you read market news
When you see "Stock X falls 8%", ask three questions: What was expected? What changed about the company's future profits? Is this about the company, its industry or the whole market? Those questions explain most moves, and they are exactly what our market stories try to answer.
