Game spreads, totals, favorites and dogs. Who covered, and how good were the Vegas lines? Breakout Live breaks down the spreads from the 2019 NFL season and busts the myth of oddsmaker predictions.
The Myth that Won’t Die
With every single passing NFL season, the final spread analysis busts one of the most popular myths about Vegas odds. Yet, no matter how often this myth is busted, fans and commentators alike continue to believe and spread the myth like gospel.
The myth I’m referring to is the bogus assertion that Vegas oddsmakers are really good at predicting the outcomes of games.
You all know what I’m talking about. You’re watching a game at the sports bar. The spread is 3 points, and the favorite is winning by 10. The underdog drives down the field and scores a meaningless, back-door touchdown with seconds remaining to push the game. Everyone exclaims, “Wow, Vegas nailed it again!”
Except that Vegas isn’t good at predicting outcomes. Not even close. And what’s more, they’re not trying to be.
Let’s start with where this fallacious belief comes from. It’s a cognitive bias known as attentional bias, which involves the tendency to pay attention to some things while simultaneously ignoring others.
Gamblers (and sports fans who follow Vegas spreads) tend to notice when a game comes down to the wire versus the spread. It adds another layer of excitement to the end of a game. Every gambler has a story about a bad beat or a lucky win, and it always involves a final game score that closely matches the Vegas spread. Since close games versus the spread always have greater emotional impact, we tend to remember them a lot more than games that are never in doubt.
Vegas Game Spreads vs. Actual Outcomes
Let’s start with how well Vegas oddsmakers did to “predict” the outcomes of games. Once again, Vegas isn’t in the prediction business, but sports fans erroneously think they are. For the purpose of this analysis, I’m using Vegas opening lines, because those are the initial oddsmaker assessments before gamblers move the lines.
Now, everyone has a different idea of what makes a good prediction. I would say a spread that comes within a field goal of the outcome is exceptional. So, was Vegas exceptional? No. Of the 267 total NFL games for the season and postseason, Vegas opening lines came within three points of the outcome 20% of the time.
Okay, let’s give Vegas a little more leeway. Let’s say a spread that comes within 7 points of the outcome is pretty decent. After all, 7 points is always just one fluky play away from a backdoor cover. So, is Vegas pretty decent at “predicting” game scores? Again, no. Vegas opening lines came with 7 points of the outcome 46% of the time – so less than half.
That means that 54% of all NFL games finished more than 7 points from the Vegas opening line. With over half the lines missing the outcome by over a touchdown, you can see why teaser bets are harder to win than one would think. What’s more, a whopping 28% of Vegas opening lines missed the final score by greater than two touchdowns!
One point of interest to gamblers: Only 10% of Vegas opening lines fell within 1.5 points of the final score. This means that, even when the closing line moves a point or a point-and-a-half from the opening line, it rarely affects whether you win or lose the bet.
Vegas Totals vs. Actual Outcomes
If you think Vegas game spreads are mediocre, wait until you see the totals. Only 18% of opening Vegas totals came within 3 points of the final score. And a paltry 39% of opening Vegas totals came within 7 points of the final score.
So yes, 61% of Vegas totals missed the actual totals by more than a touchdown. And 27% of Vegas totals were off by more than two touchdowns!
Vegas Doesn’t Do Predictions
The analysis here focuses on NFL lines, but you will find the same deviations in college football and other sports. Again, none of this is meant to criticize oddsmakers. Oddsmakers aren’t in the prediction business. They’re in the business of putting out lines that get relatively even betting on both sides, so that the sportsbook makes their vig.
In fact, if oddsmakers were superb at predicting outcomes, it would actually be bad for business. If oddsmakers regularly predicted outcomes within a few points, it would create razor thin margins for gamblers to find their spots. On the contrary, the great enticement of sports gambling is the fact that oddsmakers are so inaccurate most of the time. It gives the gambler a (usually false) sense of hope that he can regularly find his spots and beat the book.
The Real Vegas Predictions
Of course, Vegas oddsmakers are predictors of a certain kind: their job is to predict betting patterns. Their research helps them “predict” which precise line will yield relatively even betting on both sides of the bet, so the casino can ensure a profit. A line that is “off” by even just a point or two can induce lopsided betting, which can result in a big loss for the casino.
So, how well do oddsmakers “predict” betting patterns? Well, a lot better than they predict outcomes. We can gauge the effectiveness of their lines by how much the closing line moved from the opening line.
For game spreads, the closing line only moved 1 point or less 55% of the time, which would indicate very even betting on both sides. The closing lines moved 1.5 to 3 points 35% of the time, and they moved more than 3 points only 10% of the time.
For totals, the closing line moved 1 point or less 40% of the time. They moved 1.5 to 3 points 47% of the time, and they moved more than 3 points only 13% of the time.
Another important goal of oddsmaking is balancing wins between favorites and dogs. If the winning percentage swings too heavily toward favorites or dogs, bettors will discover the pattern and skew betting too far to one side.
No such problem here for the oddsmakers. Again, we’ll use opening lines to illustrate the numbers.
For the 2019-2020 NFL season, favorites covered the spread 46% of the time. Dogs covered 50%. And 4% of games pushed.
For totals, the under came in 51% of the time. Overs came in 47%. And 2% of the totals pushed. So, during the 2019 NFL season, oddmakers did a fairly good job setting lines that matched public and gambler sentiment and were excellent at setting lines that yielded even wins between favorites and dogs. But they were once again terrible at achieving the one thing they don’t care a lick about: predicting the outcomes of games.