You open an app, check your portfolio, and it's up 2%. You check again tomorrow and it's down 3%. Nothing about the companies you own has actually changed. So what's going on?

If you've ever felt a little panicked (or a little smug) watching numbers move on a screen without understanding why, you're not alone. Most people invest for years without ever getting a straight answer to this question. Let's fix that, in plain English.

It Really Does Come Down to Supply and Demand

At the most basic level, a share price (the price of one small piece of ownership in a company) moves because of supply and demand, the same force that sets the price of anything else you buy.

If more people want to buy a stock than sell it, the price goes up. If more people want to sell than buy, the price goes down. That's it. There's no secret formula running the show behind the scenes. Every other factor on this list matters only because it changes how many people want to buy or sell at any given moment.

Company News Moves the Needle

When a company releases an earnings report (a regular update on how much money it made and spent over the past few months), investors recalculate what they think that company is actually worth.

Beat expectations, and buyers often rush in, pushing the price up. Miss expectations, even by a small amount, and sellers can flood the market, pushing the price down. The same goes for other company news: a new product launch, a leadership change, a lawsuit, or a major new contract can all shift how valuable investors believe a company is.

Here's the part that trips people up: it's not just about whether the news is good or bad. It's about whether the news is different from what investors already expected. A company can report record profits and still see its share price fall, simply because investors were hoping for even more.

The Wider Economy Plays a Role Too

Stock prices don't move in isolation. They respond to what's happening in the broader economy, especially interest rates (the cost of borrowing money, set largely by central banks).

When interest rates rise, borrowing becomes more expensive for companies and consumers alike, which can slow down spending and growth. That tends to make stocks less attractive compared to safer options like savings accounts or bonds (loans investors make to a government or company in exchange for regular interest payments). When rates fall, the opposite often happens, and money tends to flow back toward stocks in search of better returns.

Inflation (the rate at which prices for everyday goods and services rise over time), employment data, and GDP growth all feed into this same picture. None of these numbers directly touch your individual shares, but they shape the mood of the entire market.

Investor Emotion: The Underrated Force

Here's something you won't always find in a textbook: markets are driven by humans, and humans are emotional.

Fear and greed move markets just as much as spreadsheets do. When everyone feels optimistic, buying tends to snowball, sometimes pushing prices higher than the underlying numbers might justify. When fear takes hold, like during a sudden piece of bad economic news, selling can snowball just as fast, sometimes dragging prices down further than the situation actually warrants.

This is why you'll sometimes see the whole market swing on a single headline, even when most companies haven't changed anything about how they actually operate that day. It's also why short-term price movements are so hard to predict. You're not just forecasting business performance, you're forecasting how millions of people will feel about that performance.

Why Day-to-Day Swings Matter Less Than You Think

If you're investing for the long term (years or decades, rather than days or weeks), daily ups and downs are mostly noise. Markets have always moved in cycles: periods of growth followed by periods of decline, followed by growth again. Zoom out far enough on almost any major market's history, and the short-term wobbles smooth into a long-term upward trend.

That doesn't mean downturns don't matter or that you should ignore risk. It means that reacting emotionally to every daily move, buying when things feel exciting and selling when things feel scary, is usually the opposite of what actually builds wealth over time. Understanding why prices move is what lets you stop reacting to the news and start making decisions based on your own plan instead.

Ready to Go Further?

Understanding what moves the market is the first step toward investing with confidence instead of anxiety. If you'd like one practical, no-jargon tip in your inbox each week to help you keep building that confidence, join Natalie's newsletter. It's free, it's quick to read, and it's designed to help you make sense of your money without the overwhelm.

This post is for educational purposes only and isn't personal financial, investment, tax, or legal advice. Market movements are influenced by many factors, and nobody can predict them with certainty. Everyone's situation is different, so speak to a qualified, regulated professional before making financial decisions.