Why News Moves Prices
A stock price is the market’s best guess about a company’s future. News changes that guess, sometimes in seconds. Here is why prices react so fast, why they sometimes jump overnight and what volume tells you about a news move.
Prices are a forecast
When you buy a share you are buying a slice of every dollar the company will earn in the future. Nobody knows those future dollars for sure, so the price is really a forecast, built from millions of buy and sell decisions. Anything that changes that forecast, such as sales, profits, a new product, a lawsuit or a change in interest rates, changes what the share is worth to buyers and sellers.
That is why news matters. It is not the headline itself that moves the price. It is how much the headline changes the market’s picture of future profits.
News shifts the balance of buyers and sellers, and the price moves to find a new balance.
Why prices react in seconds
Big investors, trading firms and computer programs read news the instant it comes out. By the time most people see a headline, the price has usually already moved. That speed is one reason we focus on understanding news rather than racing it.
Many companies release important news, like quarterly results, before the market opens or after it closes. The price cannot trade normally overnight, so the next morning the stock often opens far from the prior close. That jump is called a gap.
Gaps: when news arrives while the market is closed, the next open can be far from the last close.
A real example
In our price data, Microsoft closed at $390.54 on July 29, 2026. The next morning it opened 12.1% higher and finished the day at $451.10, up 15.5%, on about 2.8 times its average volume. In one session the market added hundreds of billions of dollars to the company’s value. Moves this size almost always follow new information, like an earnings report or an outlook change.
A real chart: Microsoft daily bars, May to Sept. 2026, with the July 30 gap. Past performance does not predict future results.
Volume tells you how much it matters
Volume is the number of shares traded. A news move on two or three times normal volume means big money is repositioning, and the new price level is more likely to stick. A move on light volume can fade just as fast as it appeared.
- Big move, heavy volume: the market is taking the news seriously.
- Big move, light volume: be skeptical; it may not last.
- Small move, heavy volume: buyers and sellers disagree about what the news means.
Key takeaways
- A stock price is a forecast of future profits.
- News moves prices by changing that forecast.
- Professionals react in seconds, so we focus on understanding news, not racing it.
- News released while the market is closed often causes gaps.
- Heavy volume shows a news move is being taken seriously.