How do sportsbooks sometimes get their odds wrong?

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Sometimes, sportsbook odds can appear too good or bad to be true. Imagine seeing Novak Djokovic win Wimbledon 2024 at 51.00 (+5000) odds. At times like these, you might want to “bet it all” to land a serious windfall. But how can major sportsbooks get their odds wrong? Please continue reading to discover some common reasons this happens and its implications on sports betting.

Where do sportsbook betting odds come from?

Betting odds are the ratio between the amount staked by a bookmaker and the bettor. So, a ratio of 50 to 1 in betting odds is expressed as 50/1 (51.00 or +5000), which means that a bookmaker will stake fifty times the amount the bettor has wagered. So with these odds, if the bettor wins, they will make fifty times their bet from the bookmaker. Odds are calculated by bookmakers like Wildz Sports by estimating the probability of an event taking place.

For example, the realistic odds of Andy Murray winning Wimbledon 2024 could be around 51.00 (+5000). These odds signal the bookmaker’s estimation that Murray’s chances of winning are low compared to the high potential payout a bettor would win if he did.

By using a mixture of in-house sports experts and advanced technology, bookies can easily monitor Andy Murray’s form and fitness, as well as that of other Tennis players. That way, bookies are usually savvy about the favourites and underdogs for tournaments like Wimbledon.

Of course, shocks can happen, like Emma Raducanu winning the US Open 2021 at odds as high as 401.00 (+40,000). In cases like this, sportsbooks weren’t wrong, so to speak. Rather, Raducanu, an unheard-of teenage qualifier, came from nowhere to stun the sporting world. In reality, a result like this wouldn’t have affected sportsbooks that much, as not many people would have wagered on Raducanu winning, let alone bet big money.

So, surprises aside, how do bookies make oddsmaking errors with so much help at their disposal?

Human error in sports betting odds

Minor details can create a big deal. A misplaced decimal point here or a typo there can have severe consequences for sportsbooks and bettors. The difference between incorrectly offered odds of 1001.00 (+100,000) and the odds of 101.00 (+10,000) can be massive. Eagle-eyed bettors could take advantage of this oversight for every second that ticks by. Tired eyes or a glitch within a sportsbook’s automated system can lead to errors taking place. It’s worth remembering that it takes humans to program technology like artificial intelligence (AI) and cloud computing. That means if there’s a mistake on the human side, it will likely be adopted and repeated by the technology.

The impact of new information and market delays

If you know about betting strategies, you’re probably familiar with expected value in sports betting. Punters can achieve expected value in sports betting by beating the closing line, i.e., getting better odds than the perceived reality.

If, by chance, Novak Djokovic and Carlos Alcaraz were to withdraw from Wimbledon 2024 a day before the tournament, Andy Murray’s previous odds of 51 (+5000) could fall to around 34.00 (+3,300) to reflect his improved chances of winning. Bettors who beat the closing line would be the ones who were able to place Andy Murray wagers at 51.00 (+5000) before sportsbooks change their odds.

Even once the tournament and matches start, in-play betting can be subject to betting odds mispricing. New circumstances, such as Jannik Sinner being 0-2 sets down to Grigor Dimitrov, will change Sinner’s odds of winning the match and the tournament as a whole. Sportsbooks that delay or forget to react to these circumstances could, depending on the outcome, display somewhat incorrect odds.

Inaccurate data models in sports betting

Anyone who knows their Tennis knows that Rafael Nadal is the King of Roland Garros. With 14 French Open titles, many outdated data sets will point to him winning it again in 2024. The reality is that a combination of age, injuries, and form limits Nadal’s chances. In addition, four or five players currently have better chances of winning the tournament. Historical data should be studied in sports betting but not taken as an absolute indicator of the future. That’s why sportsbooks relying on historical data sets, including older betting odds, could be getting it wrong.

Relying on the wrong data points

Sports are full of statistics that appeal to everyone, from mathematics nerds and professional bettors to football (or soccer) club owners. Speaking of Football, there are many ways to analyse the game and make more thought-out wagers.

Does one team usually dominate possession, and does that contribute to a win? Are other teams proficient in set pieces such as free kicks and corners, and does that help them score more goals? While these snippets of information are helpful for punters, they might need to work better for sportsbooks that rely on them.

Take expected goals (xG), for instance. Following a match, expected goals measure the quality of goalscoring chances and the likelihood of them being scored. For example, after Chelsea beat Everton 6-0, Chelsea’s xG was 3.37, and Everton’s was 1.22.

In a nutshell, it meant that Chelsea exceeded their xG, given the difficulty of some of their chances, but Everton failed to reach theirs. The issue with some statistics is using them (which some sportsbooks and punters might) to predict future results or at least the likelihood of specific outcomes.

Overwhelming favourites influencing the betting market

Despite heavy favourites not presenting a great return on the money staked for bettors, it doesn’t mean that sportsbooks can’t still lose out. Think about Wayne Gretzky’s Edmonton Oilers in 1980s NHL, the Chicago Bulls in 1990s NBA or even Tiger Woods in early 2000s Golf. Sometimes, a player or team are so dominant that most betting money will head their way.

The probability of a result multiplied by millions of dollars can make those low returns quickly add up for punters. This could leave sportsbooks vulnerable to paying out large sums if, true to form, the heavy-backed favourite does go on to win. If sportsbooks don’t change their odds to mitigate the potential financial loss, they could get their odds wrong.

Not monitoring for sports betting arbitrage

When some bettors wager on both outcomes, like the Vegas Golden Knights beating the Florida Panthers, and vice versa, in the 2023 Stanley Cup, it’s known as sports betting arbitrage or arbing. It’s a way for punters to ensure a profit by placing bets at certain odds that provide a profit across both bets regardless of the result. Because odds vary from one sportsbook to another, arbitrage bettors work quickly to identify such variations and bet on both outcomes.

Simultaneously, sportsbooks must monitor such gaps in odds and adjust theirs accordingly. If they fail to change their odds, they can display the “wrong odds” or an odds mismatch that could let arbitrage bettors pounce. From Reddit to Facebook, modern bettors have formed so many online communities. There they can share news about sportsbooks so-called incorrect odds, mistakes, bad lines or even monitor if a sportsbook fails to take down the odds for games that have already finished.

As a result, whenever a sportsbook gets their odds wrong, it rarely goes unnoticed.