Sports bettors trying to beat Over/Unders for the first time often make the same type of mistake. Whatever the sport, they’re prone to look at team scoring averages without context.
Here’s a quick recent example from the NBA. Both the Sacramento Kings and Atlanta Hawks have seen an average of around 229 points scored in their games this season (meaning the scoring sums in their games total that amount — may be a win of 115-114, a loss of 120-109, etc..). If those teams are playing each other, the novice gambler will make a knee-jerk assumption that they should total around 229 against each other.
“How easy is this?! Sacramento’s games average 229, Atlanta’s games average 229 … they’re obviously going to play to 229 against each other!”
Then the market brings an Over/Under of 236.
“Ha! Those so-called sharps are missing an easy winner. The Under is a gift!”
The Kings and Hawks played on Jan. 30 against a market total of 236, flying Over in a 135-113 Sacramento rout.
You can’t average “extreme” teams together like that. The NBA league average this season is around 221. A team that plays high-scoring games “on average” is likely to really blow up when playing another high-scoring team.
Visualize it this way. Let’s separate the league into teams that play “high-scoring” games, teams that play “average-scoring” games, and teams that play “low-scoring” games. Sacramento qualifies as high scoring this season in the high 220s. The Kings will get dragged down below that versus teams that play “low-scoring” games … will settle right around their normal 229 versus “average scoring” teams … but will blow up much higher versus other “high-scoring” teams.
The market guessed around 236 for the blow up versus Atlanta, and undershot the mark.
The same general principle is true in college basketball, college football, pro football, and hockey (baseball’s trickier because of varying pitching depth and ballpark effects). The extremes drive each other higher at the top of the spectrum, and lower at the bottom of the spectrum. That’s why you see such a volatile range of Over/Unders in those sports that skew much wider than basic averages would suggest.
Some junior-high algebra can help you make rough estimates. The formula is simply Team A’s average game scoring total times Team B’s average game scoring total divided by the league average. If you play with the numbers, you’ll see that the market is already taking this phenomenon into account.
For our Atlanta-Sacramento example, 229 times 229 divided by 221 is 237. That’s very close to what the market posted. If a pair of “low-scoring” 215 teams played each other, that formula would spit out a low 209 projection (in the general market range for games involving low scoring Indiana this season).
Betting Over/Unders isn’t as easy as it might seem … particularly if you’re a novice prone to knee-jerk reactions.