Why Betting Lines Move: A Bookmaker’s Perspective

If you hang around sportsbooks long enough, you will overhear countless conversations between bettors speculating about why a certain line has moved. Betting lines move for a variety of reasons and for the most part are in a constant state of flux. In this article, we will run through some of the main reasons why a betting line might move between the time the line opens and the start of the game.

Common Causes for Line Movement

Injuries, Rest, and Suspensions

One of the most obvious reasons you will see a betting line move is due to the absence of a key player or players. You see it on almost a daily basis in the NBA with the emergence of “load management” strategies. Players are ruled out causing lines to swing wildly as stars are rested. When a key player is suddenly expected to be absent from a game for any reason, bookmakers waste no time in adjusting their lines based on what they believe the key player is worth.

The proliferation of social media has forced bookmakers to monitor Twitter aggressively to always try and stay ahead of the professional bettors. Through the years, the amount of time between injury or rest information being released and the betting line moving has continued to decrease. Ten years ago, for instance, you might have read that the star quarterback for Ball State was injured and you would have had a couple of hours to bet the unadjusted line before it moved. These days it usually takes just a couple minutes before the line moves to reflect this type of information.

Sharp Money

Bookmakers consider sharp money to be bets that are made by winning players or players that have more information than the oddsmakers do on a given game. These bets do not always have to be for a large amount. If the person placing the bet is sufficiently respected by the bookmaker, even a smaller bet can trigger a line move. The example often given is that a player who is simply gambling could make a $100,000 wager on a game and not cause the line to move while a respected player could make a $500 bet and perhaps move the line a whole point.

Weather Conditions

Weather is one of the main reasons you will see substantial line moves on totals. In football, excessive wind, precipitation, or cold can trigger a line move of multiple points. As a general rule, before you lay your money down it’s best to check out the expected weather conditions for any games you are thinking of wagering on.

Public Money

While most of the time sportsbooks will book entirely to the sharp money that they take in, for bigger events such as the Super Bowl or March Madness, the sheer amount of recreational money being bet can dwarf the professional bettors’ wagers. This can cause lines to be moved well beyond where they otherwise would have settled by game time. Often in these situations, professional bettors will take advantage of these unique circumstances and wager heavily against the artificially inflated lines.

Handicapping Services

While most people who sell their gambling picks are not respected in the marketplace, there are a select few who actually do win. Their opinions are respected enough to move the lines, so when these groups release their picks their subscribers proceed to bet the plays as quickly as possible before the line moves.