Market movers explained: steamers and drifters

What a market mover is

A market mover is a horse whose price has changed noticeably between an earlier point — usually the first prices of the morning — and now.

Steamer

A horse whose price is shortening: 8/1 in the morning, 5/1 now. More money is arriving for it than the market expected.

Drifter

A horse whose price is lengthening: 3/1 in the morning, 5/1 now. Money is going elsewhere, or backers are laying it.

A move is a fact about the market. What it means is a separate question, and usually the harder one.

Why prices move

Some moves are driven by information. Many are not. The common causes:

• Informed money. People close to a horse — or with a good read on its chance — back it. This is the move everyone hopes they are looking at.
• Weight of opinion. A newspaper nap, a tipster with a big following, or a horse with a popular jockey can shorten on public money alone.
• A single large bet in a thin market. Early in the day, markets on smaller races can move a long way on relatively little money.
• Bookmakers managing liabilities. A firm that has laid a horse heavily may shorten it to discourage more bets, whatever it thinks of its chance.
• Non-runners. When a horse is withdrawn, the rest of the field's prices shorten to fill the gap — a move that reflects arithmetic, not opinion.
• The whole market tightening. As a race approaches and more money arrives, prices across the field can firm together. A move shared by most of the runners is not a gamble on any of them.

How a move is measured

Every move has a starting point and an end point, and both matter.

• Starting point. Overnight prices, the first bookmaker show in the morning and the early exchange market are all different. A horse can "steam" from a price that was only available for a few minutes to a handful of people.
• End point. The current exchange price, the current best bookmaker price and the starting price can all differ.
• The percentage. The usual figure is the change in decimal price. From 9.0 to 6.0 is a 33% shortening.

That percentage hides something important: the same percentage move means very different things at different prices, because what matters is the change in probability.

Context: how much money, and when

A move on a busy afternoon market with tens of thousands matched is a different thing from a move overnight on a few hundred pounds. Before reading anything into a move, check:

• How much has been traded on the horse and the race.
• When it happened. Early moves in thin markets are more easily caused by a single bet; late moves in deep markets involve more money.
• Whether the rest of the race moved too. Compare the horse's move with the field's.
• Whether anything else changed — a non-runner, a jockey switch, the going.

What a move can and cannot tell you

A price move tells you that the market's opinion has changed. In most betting markets, prices tend to become more accurate as more money and information arrive before the off, which is why moves are worth knowing about.

It does not tell you:

• who moved the price or why;
• whether the new price is right — a steamer can be overbet, and a drifter can end up at a price that is too big;
• that backing horses after they have shortened is profitable. By the time you see the move, the new price already includes it.

So treat a move as one more piece of evidence about a horse, weighed alongside the form — not as a verdict.

Common mistakes

• Chasing the price. Taking 3/1 about a horse because it was 6/1 this morning means taking the worse price for the same horse.
• Treating every percentage the same. A 25% move on a 20/1 shot is a far smaller change of opinion than a 25% move on an even-money favourite.
• Ignoring volume. A big move on a small amount of money is fragile.
• Reading drifts as a stable "not trying". Most drifters simply had less money for them than expected.
• Counting it twice. If a score or a tip already includes the market price, a market move is not independent evidence on top.

How TRF measures market moves

TRF measures every move from the morning price to the live Betfair Exchange price, as the percentage change in decimal odds. On the racecards, prices refresh every 30 seconds and carry a label saying how old they are, and opening a runner shows its move — morning price to now, with the amount matched.

Smart Money collects the day's movers: steamers (runners flagged by our market feed or shortened by 15% or more) and drifters (lengthened by 10% or more). Overnight, it lists horses that shortened by 20% or more from the 8pm price on at least £500 matched, flags moves on thin trading or where the whole race moved together, and separately shows the most-traded runners whose price held.

These are reports of what the market did, not selections. The AI Score on each runner never uses live price moves, so it stays an independent read of the form.