Eagerness, not logic
A price rises when more people are eager to hold shares at the current price than current holders are willing to part with — so those wanting shares raise their bids. It falls when the reverse is true. Every single tick is this balance tipping, one way or the other. It is not a judgment about what is “right.” It is a negotiation result.
News changes the balance
An earnings report, a product launch, an economic number — news changes what people believe the business will become worth, which changes how eager they are. Note carefully: it is the reaction to news that moves the price, not the news itself. News that everyone already expected often moves nothing at all, because the eagerness already adjusted days ago. This is why “good news, price falls” happens constantly and confuses beginners: the news was good, but the positioning ahead of it was even more optimistic. The price responds to the gap between expectation and reality, never to the headline in isolation.
The order book, in plain words
Behind every price sits a stack of unfilled orders: bids lined up below the current price, asks lined up above it. When a wave of orders arrives, it works through that stack, and the price jumps to wherever the stack can absorb it. A deep stack absorbs waves calmly. A thin stack means one large wave can move the price a long way. You can watch this stack live on most brokerages — it is called level 2 or the order book — and seeing it once teaches more than any description: the “price” is just the meeting point of two visible queues.
Why it never sits still
Thousands of participants reassess constantly — new information, shifting moods, and automated strategies reacting to each other. The balance of eagerness is renegotiated every second the market is open. Stillness would require everyone to agree, and they never do.
How much changes hands matters
Not all price moves are equal. A price that rises while enormous numbers of shares change hands means broad agreement — many participants repositioned at once. A price that drifts on tiny volume means almost nobody participated; the move carries little information. Professionals watch this relationship closely: price tells you what happened, and the amount of shares involved tells you how much weight to give it. Neither predicts anything — but together they describe the move more honestly than price alone.
What this cannot tell you
Understanding the mechanism does not mean predicting the next move. Mechanics describe how prices move; they say nothing about where prices go next. That distinction matters more than anything else on this page: this is an explanation of plumbing, not a forecast.
Between sessions: the open and the close
Prices also move when the market is closed. News breaks overnight — earnings released after hours, events overseas — and by the time the opening bell rings, eagerness has already shifted. The opening price is simply the first new negotiation, and it can sit far from the previous close. The same thing happens in reverse at the close: the final minutes often see a burst of orders as participants position for the night. Two practical notes follow from this. First, a price that “gapped” overnight did not travel through the prices in between — nobody transacted there. Second, orders left open overnight can complete at prices you never saw coming, which is why limit orders exist.
Worked example: One order moving the price
Illustrative figures only, to show how the order stack absorbs orders.
| Price | Shares in the stack | |
|---|---|---|
| Bids | $50.00 | 500 |
| Bids | $49.95 | 800 |
| Asks | $50.05 | 300 |
| Asks | $50.10 | 600 |
A market order for 400 shares takes all 300 at $50.05, then 100 at $50.10. The ask is now $50.10 — the price moved on a single order, because the stack at $50.05 was thin.