Why betting odds move before kick-off
Odds move for three reasons: news, money and time. What each one means, why the price near kick-off is usually the best informed, and what it means for you.
Betting odds move before kick-off because the price is an opinion that keeps learning. Three things teach it: news (injuries, line-ups, weather), money (who is betting, and how much) and time (as the match gets closer, more of both arrives). By kick-off the price has usually absorbed most of what there is to know, which is why the closing price is the hardest one to beat.
News
This is the one everyone understands. A striker is ruled out, a goalkeeper fails a fitness test, a pitch freezes, and the chance of each result really does change. The price follows.
The timing is what catches people out. Some news is public days ahead; some arrives an hour before kick-off with the team sheets. Our own example this week: Lyon's Moussa Niakhaté picked up a hamstring injury on international duty before the trip to Lens. Any price posted before that news was a price without it. We cover what a break does to prices in what an international break does to the odds.
Money
Bookmakers do not only set prices; they react to bets. Steven Levitt's 2004 study of a betting market found that bookmakers do not simply balance the money on both sides. They set prices from their own view and lean them against where they expect casual money to go. So a move is not always a crowd stampede.
What matters more than the amount is the source. A bookmaker treats a bet from an account with a long record of beating its prices very differently from the same stake from an account that loses. One large, respected bet can move a line further than a thousand small ones. Exchanges, where customers bet against each other, show the same thing in plain sight.
Time
Opening prices are set early, with less information and usually lower limits on how much anyone can stake. As kick-off gets closer the limits rise, more informed money arrives, and other bookmakers copy whoever moved first. Forrest, Goddard and Simmons found in 2005 that bookmakers' odds on English football were strong forecasts, holding their own against a detailed statistical model. The price near the start carries the most information it ever will.
That is why we treat the closing price as a scoreboard, explained in why the closing line is a useful scoreboard.
What it means for you
If you think a price is wrong, the question is whether you know something the market does not, or simply know it sooner. Once news is public, assume the price will reflect it shortly. And an edge measured against an old price is only as good as that price still being there; see what a positive edge actually means.
What this does not tell you
It does not tell you which way any price will move next, or that every move is informed: some are noise, and some are a bookmaker managing its own risk. It also does not mean the closing price is always right. It is the best informed, which is not the same thing.
Common questions
Why do betting odds change before a match?
Because the bookmaker learns things. Team news arrives, money comes in on one side, and other bookmakers and exchanges move. Each one is new information, and the price adjusts to it.
Do odds move because of how many people bet?
Partly. Bookmakers watch where the money goes and who is placing it. A large bet from an account they respect moves a price more than many small ones from accounts they do not.
Is the price just before kick-off more accurate?
Usually, yes. By then most of the news and money is already in the price, and research on English football finds bookmakers' odds are strong forecasts. That is why beating the closing price is a useful test.