Why Sportsbooks Almost Never Predict MLB Winners Correctly
April 22, 2021
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When baseball season starts, the earliest bets that come in are futures bets, which are wagers on the World Series winners. Usually, the odds on long-shots are as high as they’re going to be. Futures odds in the low to mid-thousands tend to decrease from the preseason through the World Series. However, futures odds at the beginning of the season are a bad guide to who will win the World Series. In fact, one of the best ways to guess who will win the World Series is to bet against the most favored teams.
And we have the data to prove it.
The first lesson you should take away from this table is that most World Series winners have long odds during the preseason. About a third of the winners are in the +400 to +900 range at the start. But almost half of all World Series winners have odds between +900 and +4900. Sportsbooks and sports journalists do not predict World Series winners well.
Only five teams had odds lower than +400 during the preseason – and two of them were the Yankees during their late-‘90s hot streak. Excluding those two, that’s as many calls as championship teams with odds above +4900. Winners can come from anywhere, but they usually come from teams that no one’s expecting during the preseason.
So what gives?
History Doesn’t Lie
There’s a great site that archives sports betting odds from previous years. Their data set on MLB futures odds go all the way back to 1985. So, we can see how well sportsbooks guessed the World Series winners from 1985 to 2020. They don’t do great. Out of 35 years, here’s how many teams were in different groups of odds:| Odds Range | Implied Probabilities | World Series Winners In Odds Range | Overall Percentage |
| +100 to +400 | 50%-20% | 5 | 14% |
| +400 to +900 | 20%-10% | 11 | 31% |
| +900 to +1900 | 10%-5% | 7 | 20% |
| +1900 to +4900 | 5%-2% | 9 | 26% |
| Over +4900 | Less than 2% | 3 | 9% |
