How Stock Prices Move

Share prices look erratic from the outside — up 3% on a day of bad news, down 8% on a day of record profits. They are not erratic. They follow a rule that is simple to state and genuinely hard to internalise.

Prices move on the gap between what investors expected and what actually happened — not on whether the news was good or bad in absolute terms. This lesson works through what that means in practice.

What is a Stock Price, Really?

At its simplest, a stock price is the most recent price where a buyer and seller agreed to trade.

Think of it like a photograph. It captures a single moment in time. It is not a permanent tattoo on the company’s soul, nor is it a guaranteed promise of the future. A price simply tells you what the market is willing to pay right now for a slice of that company.

The Mechanics of a Trade

To understand price, you have to look at the bid-ask spread.

• The bid: the highest price anyone is currently willing to buy at. If you want to sell right now, this is what you get.
• The ask (also called the offer): the lowest price anyone is currently willing to sell at. If you want to buy right now, this is what you pay.
• The last price: where a trade actually went through. This is the number quoted as "the price".

Note that "ask" and "offer" are two words for the same thing — the sell side. UK brokers tend to say "offer"; US sources tend to say "ask". Neither means the bid.

When expectations change, the bids and asks move, and the last traded price follows.

The Core Driver: Expectations, Not Events

The most important lesson you will learn in finance is this: Markets are forward-looking.

Stock prices move when reality differs from what was already expected. They don't move because something happened; they move because something surprised us.

How the Surprise Works

Imagine a restaurant chain you follow announces a new menu. If the menu is exactly what you expected, the stock price of the restaurant (or its parent company) might not change much. But if the menu is way better than you hoped, or if it’s a disaster, the price will jump or drop.

Let’s look at how this plays out with numbers, a scenario known as "Beating or Missing Estimates":

1. Earnings beat expectations: the company makes more than analysts forecast.
   • Result: The price usually rises.
2. Earnings beat, but by less than hoped: profits grew, just not as much as the market had quietly priced in.
   • Result: The price usually falls.
3. Earnings miss, but the outlook improves: this year disappointed, but management upgrades guidance for next year.
   • Result: The price might rise.

See? It’s not about the raw numbers; it’s about the gap between the numbers and the prediction.

The Expectation Gap Framework

To master this, you need to understand the "Expectation Gap." It is the space between what the market believed would happen and what actually happened.

• Consensus Expectation: What the "smart money" and the average investor collectively believe will happen.
• New Information: The actual results, news articles, or government data.
• The Gap: The difference between the two.

This explains why a fantastic company can sometimes see its stock price drop. It’s not because the company is failing; it’s because the stock price was already priced for perfection. When reality matches the perfection, there is no excitement, just a flat line.

The Invisible Hand: Supply, Demand, and Liquidity

Information alone doesn't move prices. There is a second force at play: Liquidity. This is simply how easily you can turn an asset into cash without dropping the price.

Imagine you want to sell a rare comic book. You might have to wait a long time to find a buyer, and you might have to accept a lower price to get someone to take it off your hands quickly. This is low liquidity.

Now imagine you want to sell a crate of apples. You can find a buyer in seconds for the market price. This is high liquidity.

• Low Liquidity: Prices can swing wildly on very small trades.
• High Liquidity: Prices are more stable; it takes a lot of money to shift them.

Who is Moving the Market?

It is easy to feel like the market is controlled by a cabal of wizards. In reality, it is a mix of different players, and they all have different motives.

• Retail Investors (You and Me): We trade based on news, tips, and emotions. We have high participation but smaller amounts of money. We tend to move the needle in smaller, less popular stocks.
• Institutional Investors (Banks, Pension Funds, Hedge Funds): These are the heavyweights. They manage trillions of pounds and dollars between them. They trade based on complex models, mandates, and risk management. When they buy or sell, prices move significantly.
• Market makers: firms that quote a buy and a sell price simultaneously and stand ready to trade with anyone. They aren't neutral officials — they're trading their own capital, and they earn the spread between the two prices in return for carrying the inventory risk. They widen that spread when a share becomes volatile or hard to hedge.
• Passive Investors (ETFs): These are index funds that just buy everything in an index automatically. They don't care if a company is "good" or "bad"; they just follow the rules.

When you hear "the market thinks," it usually refers to the collective positioning of the Institutional Investors.

Time Horizons: Don't Use a Hammer to Swat a Fly

Different investors look at the clock differently. This causes a lot of confusion.

• Short-Term (Days/Weeks): Driven by News and Flows. Traders are reacting to headlines, rumours and technical patterns.
• Medium-Term (Months): Driven by Revisions and Narratives. Investors are asking, "Is the business story getting better or worse?"
• Long-Term (Years): Driven by Fundamentals. Are the company's profits growing? Is the debt manageable?

The biggest mistake beginners make is looking at a short-term chart and trying to apply long-term logic. A stock might drop 50% in a day due to a bad headline, even though the company is fundamentally strong. Conversely, a great company can stagnate for years because the market thinks it can't grow any faster.

Volatility Is Not Direction

We often hear people say, "The market is so volatile!" But volatility doesn't tell us if the market is going up or down. It only tells us how uncertain the market is.

• High Volatility: Expectations are unstable. Nobody agrees on what the stock is worth. The price is bouncing around like a pinball.
• Low Volatility: Expectations are aligned. The market broadly agrees on what the share is worth, and the price stays in a narrow band.

Why Headlines Often Feel Wrong

This is perhaps the most frustrating part for beginners. You see a scary headline, expecting the stock to crash, but it actually goes up. Why?

Because Markets react to what is already priced in.

By the time a news story hits your phone or TV screen:

1. The big institutions have already analysed the data.
2. They may have already bought or sold the stock based on that analysis.
3. The price movement has likely already happened.

Markets often look irrational because they react to information before the general public even realizes the information exists. The public sees the result; the market sees the cause.

Common Misconceptions

Three myths worth clearing up:

• "Good companies always go up." False. A "good" company can be overvalued. If you pay £100 for a £10 note, it is still a perfectly good £10 note — and still a terrible purchase.
• "Bad news always causes sell-offs." False. Sometimes bad news removes uncertainty. If a company is in trouble, a "bad" result might be better than the terrifying unknown.
• "Stock prices follow fundamentals." Incorrect. Stock prices follow changes in expected fundamentals. The price doesn't care about the past; it only cares about the future.

Summary

To wrap this up, here are the key takeaways to remember:

1. Price is a Snapshot: It is the price of the last trade, not a judgment on the company's soul.
2. Expectations Rule: Prices move based on the gap between what was expected and what happened.
3. Liquidity Matters: It takes more money to move a big company's stock than it does a small one.
4. News is Old News: By the time you see it, the price has likely already reacted.
5. Short vs. Long: Don't use a long-term strategy to fix a short-term problem.

Once you read a price move as a shift in expectations rather than a verdict on the company, the market stops looking arbitrary. A share falling on good news isn't the market being irrational — it's the market telling you the news was already in the price.