If you’ve ever checked a share price in the morning and noticed it changed by the afternoon, you might wonder:
Who decides the price?
Is it the company?
Is it the government?
Is it random?
The answer is much simpler than most people think.
Share prices move because of supply and demand.
Let’s break it down clearly.
What Controls Share Prices?
On the Australian Securities Exchange, prices are determined by buyers and sellers.
When you place a buy order, you are offering a price.
When someone places a sell order, they are asking for a price.
When those two match — a trade happens.
That matching process determines the current share price.
Supply and Demand Explained
If More People Want to Buy (High Demand):
- Buyers compete with each other.
- They offer higher prices.
- The share price rises.
If More People Want to Sell (High Supply):
- Sellers compete with each other.
- They accept lower prices.
- The share price falls.
That’s it.
There’s no secret formula — just market participants reacting to information.
Simple Example
Imagine a company’s share is trading at $20.
If:
- 500 people want to buy
- 200 people want to sell
Demand is stronger than supply.
Buyers may increase their offer to $21.
The price moves up.
Now imagine:
- 200 people want to buy
- 800 people want to sell
Sellers outnumber buyers.
They may drop their price to $19.
The price moves down.
What Causes Demand to Increase?
Demand usually rises when:
- The company reports strong profits
- The economy is improving
- Interest rates fall
- The industry outlook improves
- Investors feel confident
Positive news = more buyers.
What Causes Selling Pressure?
Supply increases when:
- The company reports poor earnings
- The economy slows
- Interest rates rise
- Investors panic
- Global markets fall
Negative news = more sellers.
The Role of News
Markets react quickly to information.
For example:
If a mining company announces a major new discovery, investors may rush to buy.
If a bank reports lower profits than expected, investors may sell.
The share price adjusts almost instantly.
Markets are forward-looking — prices reflect expectations about the future, not just current performance.
Market Orders vs Limit Orders
Prices also move based on the type of orders placed.
Market Order
You agree to buy or sell at the best available price.
This can move prices quickly in volatile markets.
Limit Order
You set the maximum price you’re willing to pay (or minimum to sell).
This adds structure to the order book.
What is the Order Book?
The order book shows:
- All buy orders (bids)
- All sell orders (asks)
The highest bid and lowest ask determine the next possible trade.
When they meet — the trade executes.
Why Do Prices Move Every Second?
Large investors, super funds, traders, and retail investors are constantly:
- Analysing data
- Reacting to news
- Adjusting portfolios
- Managing risk
That constant activity creates price movement.
Even small changes in sentiment can cause noticeable swings.
Volatility – Fast vs Slow Movement
Some shares move slowly.
Others are very volatile.
Volatility depends on:
- Company size
- Trading volume
- News sensitivity
- Market conditions
Small companies often move more sharply than large ones.
Example Using the Index
If many large companies fall in one day, the
S&P/ASX 200 may drop.
This doesn’t mean every company fell — but it shows overall selling pressure in the market.
Indices reflect collective price movements.
Do Companies Control Their Share Price?
No.
Companies control:
- Business performance
- Strategy
- Profitability
But investors decide:
- How much the company is worth
- Whether to buy or sell
The market sets the price.
Can Share Prices Be Manipulated?
In Australia, strict regulations prevent illegal manipulation.
Authorities monitor trading activity to detect:
- Insider trading
- Artificial price inflation
- Market misconduct
While short-term speculation exists, the long-term price usually reflects business performance.
Short-Term vs Long-Term Movement
Short-term prices may move because of:
- Rumours
- Headlines
- Technical trading
- Emotional reactions
Long-term prices move because of:
- Earnings growth
- Revenue growth
- Competitive advantage
- Economic expansion
Serious investors focus on long-term fundamentals.
Why Understanding Price Movement Matters
If you don’t understand why prices move, you may:
- Panic when prices fall
- Get greedy when prices rise
- Make emotional decisions
When you understand supply and demand, you become calmer.
Price movement becomes logical — not scary.
Simple Scenario
You invest $1,000 in a company.
Week 1: Price rises 5%.
Week 2: Price drops 3%.
Week 3: Price rises again.
This fluctuation is normal.
Markets breathe — they don’t move in straight lines.
Key Terms to Remember
Supply – Number of shares available to sell
Demand – Number of shares investors want to buy
Bid – Price buyers are offering
Ask – Price sellers want
Volatility – Speed of price movement
Market sentiment – Overall investor mood
Final Thought
Share prices move because people make decisions.
When confidence is strong, prices rise.
When fear increases, prices fall.
The market is simply millions of decisions happening at once.
Understanding this is the foundation of becoming a disciplined investor.
Before investing real money, practise in a simulator and observe how prices react to news and demand changes.