Betting odds change for three main reasons: news changes the chance of a result, money leaves a bookmaker exposed if one outcome wins, and bookmakers move to match the exchange or each other. With illustrative prices, a team that shortens from $3.00 to $2.50 has gone from an implied 33.3% chance to 40.0%, and which of the three caused it decides what the move tells you.
Money and copying can move a price with no news at all, so telling the kinds of move apart turns a price history into evidence a betting strategy can use, instead of a reason to chase.
Odds shortening and drifting: what a move means
Odds shortening means the price gets smaller, so the result pays less and the market rates it more likely. Drifting is the reverse. Turn each price into an implied chance, 1 / price, to see how far the market's view moved. With illustrative prices:
| Move | Implied chance before | Implied chance after | Change |
|---|---|---|---|
| $3.00 to $2.50, shortening | 33.3% | 40.0% | +6.7 points |
| $1.65 to $1.90, drifting | 60.6% | 52.6% | -8.0 points |
Each implied chance still carries the bookmaker's margin, so read the points as the size of the move, not as true chances; the odds converter turns any price into one. Horse racing flucs shows how to read a whole price history.
A move after you bet does not touch a fixed-odds bet already accepted: it keeps its price. Two Australian exceptions matter. A winning fixed-odds racing bet struck before a late scratching is paid less a deduction the stewards declare. Tote and starting price bets are settled on the final pool or the official price, so they move with the market until it closes.
News: team changes, scratchings, track and weather
News moves a price because it changes the chance itself. The main Australian triggers:
| News | When it lands | What moves |
|---|---|---|
| Team selections, injuries and late changes | AFL and NRL teams are named a day or more before a game, and changes can follow up to the start | The player's own markets first, then head to head, line and total; a market may be suspended while it is priced again |
| Late scratchings | After betting has opened, often on race day | Every runner in the race, as the market is re-framed |
| Track rating changes | Before and during a meeting, as rain falls or a track dries | Runners suited by the new rating, against the rest |
| Weather | On the day | Totals, and whichever side the conditions suit |
AFL team announcements, NRL team lists and track ratings set out when each kind of news lands.
A late scratching moves prices with no money behind them. Racing NSW's deductions policy describes the method that took effect on 1 August 2011 in NSW, the Northern Territory, Queensland and Victoria: an algorithm that re-frames the market to the percentage it had before the withdrawal (checked October 2026). The simplest version of that idea scales every remaining chance by one factor. In an illustrative eight-runner race at $3.00, $4.00, $5.00, $8.00, $11.00, $15.00, $21.00 and $34.00, adding 1 / price across the field gives a market of 114.3%. Scratching the $5.00 runner (20.0%) leaves 94.3%, a factor of 114.3 / 94.3 = about 1.212:
| Price before | Implied chance before | Implied chance after: x 1.212 | Price after: price / 1.212 |
|---|---|---|---|
| $3.00 | 33.3% | 40.4% | $2.48 |
| $4.00 | 25.0% | 30.3% | $3.30 |
| $8.00 | 12.5% | 15.2% | $6.60 |
| $34.00 | 2.9% | 3.6% | $28.05 |
Every runner shortens, and nobody backed any of them. The stewards' method can weigh runners differently from this simple scaling; scratchings and deductions covers bets already struck.
Weight of money and the bookmaker's liability
Money moves prices even when nothing about the game has changed, because a bookmaker also prices to limit what any one result would cost it, its liability. With illustrative numbers, a bookmaker opens a game at $1.80 for Team A and $2.05 for Team B, a market of 1 / 1.80 + 1 / 2.05 = 104.3%. It then takes $30,000 on Team A and $12,000 on Team B:
| If this team wins | Paid out | Bookmaker's result on the $42,000 taken |
|---|---|---|
| Team A | $30,000 x 1.80 = $54,000 | -$12,000 |
| Team B | $12,000 x 2.05 = $24,600 | +$17,400 |
To stop the gap growing, the trader shortens Team A to $1.72 and lengthens Team B to $2.15, a market of 1 / 1.72 + 1 / 2.15 = 104.7%. Team A's implied chance rises from 55.6% to 58.1% with no news at all. If the next $10,000 comes for Team B at $2.15, the bookmaker has taken $52,000. The book then stands at $52,000 - $54,000 = -$2,000 if Team A wins and $52,000 - ($24,600 + $10,000 x 2.15) = +$5,900 if Team B wins, far closer to level.
So a shortening price can mean informed money, or simply a lot of money on a popular side. On an exchange, which has no bookmaker's book, traders read the same pressure as weight of money: the offers queued on each side. A steam move, a sharp shortening across the whole market at once, is the kind most often read as informed money.
Bookmakers following other markets
Plenty of prices move because another market moved first. A follower takes a reference, such as the exchange or a bookmaker that tends to move early, and adjusts its own price afterwards, sometimes minutes later. With illustrative prices on Team A after team news breaks:
| Time | Exchange back price | Bookmaker A | Bookmaker B |
|---|---|---|---|
| Before the news | $1.92 | $1.87 | $1.87 |
| 1 minute after | $1.75 | $1.87 | $1.87 |
| 2 minutes after | $1.75 | $1.72 | $1.87 |
| 5 minutes after | $1.76 | $1.72 | $1.73 |
For several minutes Bookmaker B's $1.87 sits well above the exchange, a price that has not caught up and can be cut before a bet on it lands. When it shortens, that is a follower catching up, not new information. Sharp vs soft bookmakers covers who tends to lead, and how bookmakers set odds why so many prices follow a reference.
Why early markets move more than late ones
An early market has the least information and money behind it. Its first prices are a compiler's estimate or a copy of another early price, and a bookmaker has reason to keep stake limits low while it is least sure. So the first real bets and news can move it a long way. Early race markets can also carry a bigger margin that shrinks as the jump nears, lengthening several prices together with no news or money: market percentage shows how to check.
Take an illustrative AFL line. It opens on Monday at Team A -4.5, moves to -8.5 after the week's team announcements bring two of Team A's best players back, and closes at -9.5 before the first bounce. Most of the move came from news that did not exist when the market opened. A punter who took -4.5 on Monday holds a line 5 points better than the close; one who bet on Friday paid for the news.
Late markets still move, but each move has more money and news behind it, which is why the last price before the start is the usual benchmark for closing line value. Racing bodies can also set when race markets must be up. From 1 July 2025, Racing Queensland's conditions have required wagering operators to publish markets for Queensland TAB meetings in all three codes by 10am on race day (checked October 2026).
Risk: Betting involves risk. An early price can beat the close or lose to it, because the news that follows can go either way. See responsible gambling for limits and support.
Reading a move: information or noise
No price tells you why it moved, but a few checks separate betting odds movement driven by news from noise:
| Check | Points to information | Points to noise |
|---|---|---|
| Who moved | The exchange and several bookmakers together | One bookmaker on its own |
| What happened | A team change, scratching, rating change or injury you can name | Nothing you can find |
| Did it hold | It stayed, or kept going | It bounced back within minutes |
| How big | Several points of implied chance | A tick on a long price |
| When | Near the start, with plenty of money in the market | Hours out, in a thin market |
| What kind of price | A standard market price | A boosted price or a promotion on one bet |
A move that ticks most of the left-hand column is information, and by the time you see it, it is in the price: backing at the new price means a shorter price for the same chance. Reverse line movement, a price moving against the side most bets are on, depends on counts of bets on each side that are not usually public, so treat claims built on it with caution.
Mistakes when odds move, and what they cost
| Mistake | What it costs, with illustrative prices |
|---|---|
| Backing a runner after it firms from $4.00 to $3.20 because the money must know | If $3.20 is now the right price there is no edge left; a punter who took $4.00 earlier holds a price 4.00 / 3.20 - 1 = 25% above it |
| Taking one bookmaker's cut as news | Its $2.60, when others still offer $2.80, pays 1 - 2.60 / 2.80 = 7.1% less on a winner, for no new information |
| Backing a drifter because it was shorter this morning | The morning price had less information in it, so the drift can be the market correcting it |
| Raising your stake to get on before a move | More money on a price you have not checked: set the stake before you look at the moves |
Risk: Betting involves risk. A better price is not a result: a $4.00 bet on a runner now at $3.20 can still lose. See responsible gambling for limits and support.
Watching odds move on B337's Terminal
On B337's Terminal, prices from 40+ bookmakers across racing and sports sit side by side, beside Betfair back and lay and the closing lines. Each price's history (flucs) shows whether it is firming or drifting, and the Betfair prices show where it sits against the exchange. Prices are read on a repeating cycle, not tick by tick. A price on screen can trail the bookmaker's own, so confirm it with your bookmaker before you bet.
A free account opens a limited view of the Terminal with live odds; Betfair prices and closing lines start with Terminal View, as pricing sets out. Betfair is a trade mark of its owner, and B337 is not affiliated with it. Bookmaker names are trade marks of their owners. B337 is not affiliated with them.
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Risk: Betting involves risk. A price history shows where a market has been, not what will win, and a move you spot on screen can already be gone at the bookmaker. See responsible gambling for limits and support.