Sportsbooks are more reactive than proactive. After gathering experts to set an initial betting line, the oddsmakers’ jobs are not close to being done. From the moment a line is released to the public, oddsmakers are reacting to external forces and changing the lines by use of movements.
Line movements are the changes to an initial betting line in reaction to several external events, and they can be in either direction. Sportsbooks can manually adjust these lines at liberty to better reflect the true odds. While they may seem unpredictable at times, there are actually several concrete reasons why betting lines move. Additionally, there is a way to predict their movements with some precision. If bettors can collect enough data, they can alter betting strategy to gain value on a bet before the line moves.
Follow the Money
The main reason sportsbooks move their lines is the main reason any company does anything: to make a profit. There is a general fallacy that exists among the betting community that “Vegas” can lose on its bets. You’ll always hear after an upset, “Wow, Vegas lost a ton on that one. Nobody expected that underdog to win.” This couldn’t be further from the truth.
“Vegas” makes its money by charging a vig, approximately 10 percent of the wager depending on the sportsbook, on all of its bets. Then, it ensures it gets as close as possible to an equal amount of money on each side of the bet. This way, when the game begins and bets are off, the sportsbook has close to zero exposure to the actual outcome. They take their percentage of the total wager and walk away knowing they’ve already won.
For example, let’s say a sportsbook puts out the line for the Super Bowl at Chiefs -1 vs. 49ers. If more money is coming in on the Chiefs’ side than the 49ers’ side, they will raise the line to Chiefs -2 to entice the public to bet the 49ers. If it sways too much in either direction, the sportsbook will adjust the line accordingly. Overall, line movements are the sportsbook’s response to the money coming in on each side in an effort to ensure they have zero exposure tied to the outcome.
Now, how can this help in your betting strategy and give you an insight into line movements? You can follow the money. It is difficult for sportsbooks to operate cohesively in real-time, which is why you’ll see different odds among the many sportsbooks. If you see one sportsbook changing their lines after receiving heavy action on one side, you can get value at another sportsbook before they change their odds. Eventually, all lines typically end up within 0.5 or 1 point of each other, so getting the value before the other sportsbooks have time to adjust is key.
The Favorite Will Jump First
Typically, the line will tend to move toward the favorite after the initial lines are set. For example, if the Lakers are favored over the Warriors by six points when the odds are released, the public is more inclined to bet the favorite early. The sportsbook will then adjust their line accordingly and raise the Lakers to either a seven or eight-point favorite depending on the amount of money they receive.
The main thought process behind this trend is that there is a psychological tendency among the non-professional bettors to take the favorite. The spread doesn’t mean much to them, but they know that the Lakers are better than the Warriors, so they’ll put money on the Lakers regardless of the number next to them at the outset. They figure the lines must make it 50/50 upon its release, so they’ll put money on the favorite early.
Given this trend, you can gain value on either the favorite or underdog depending on which one you prefer. If you like the initial odds on the favorite, you should bet them immediately and gain the value before it moves. If you like the underdog, let some time pass, and the line should move toward the favorite, giving the underdog more points.
Knowing that the public will more likely jump on the favorite early creates an advantage for bettors to gain value on the side they like most. While this method is not infallible because the tendencies of others are unpredictable, more often than not, this trend holds. If you want to predict which way the line will move and gain value on your bet, the rule of thumb that the favorite will jump first is a good place to start.
Keep an Eye on Injuries
Another factor that causes betting lines to move is injury. When a key player for either team suffers an injury, suspension, or any circumstance where they would miss a game, the line will move in response to how this will affect the team’s competitiveness. For some players, the number may only be half of a point. But for big names like LeBron James or Tom Brady, lines could sway multiple points. This could create an advantage for the keen observer.
Now, I am not saying you can predict when an injury is going to happen. But sportsbooks are not in the guessing business; they are in the information business. They will move the lines when concrete information comes in. We, as bettors, are in the prediction business, using whatever data is available to make appropriate assumptions that can provide a competitive advantage. This is why you must keep a close eye on player performance, playing time, and press conferences.
For example, in the 2019 NFL season, Panthers quarterback Cam Newton played the first two games of the regular season. In Week 2, if you watched the game, Newton looked like he couldn’t move. His throws were extremely inaccurate, he couldn’t run the ball, and he was wincing in pain. If that eye test wasn’t enough, the Panthers gave you one last sign that Newton was not healthy. With a chance to win it from the opponent’s one-yard line, the Panthers motioned Newton out of the play and directly snapped it to their running back Christian McCaffery. Nine times out of ten, a healthy Cam Newton takes it himself and runs it in.
Even though head coach Ron Rivera stressed after the game that Cam Newton was not injured, anyone who watched would’ve known better. However, sportsbooks can’t move the line off of a guess. The Panthers opened next week as a three-point favorite against the Cardinals with a 46.5 over/under. That line stayed relatively steady until news came out six days after the Week 2 contest that Newton would miss the Week 3 matchup. The line closed with the Cardinals as a 2.5-point favorite and the over/under dropped to 44.5. Cam Newton’s health caused the spread to swing six points and the over/under to dip two points.
For bettors who believed that backup quarterback Kyle Allen was inferior to Cam Newton, as most of the general public did, they could’ve had an advantage by betting the Cardinals +2.5 and the under 46.5 before the news became official. While it turned out Allen was much better than expected and the Panthers covered the spread and the over, the result doesn’t change the process.
Bettors who kept a keen eye out for injuries by watching the game, press conferences, and practice reports could make a fair prediction that Cam Newton would miss the game, and the line would drop accordingly. From there, it’s up to the bettor how he or she would like to take advantage.
Watch for Weather
Weather is another external force that impacts betting lines. While it mostly will affect both sides evenly from a point spread perspective, inclement weather will have an impact on the over/under bets. As the weather gets more treacherous, the game total will start to decline as people expect it to affect scoring.
Now, I am not saying you can predict the weather. Meteorologists are paid to do this for a living, and even they are inaccurate much of the time. However, if you keep an eye on weather reports and such, you may be able to take advantage of knowing the weather won’t be ideal for a game. This impact mainly concerns NFL games, as many are played outdoors regardless of weather conditions.
Predicting that there would be inclement weather during an NFL game would allow one to potentially anticipate a downward movement in the total line. A bettor could take advantage by betting the under when the line was at its peak and obtain a “cushion” as the actual line dropped before game-time. Increased data and accurate predictions using said data could create a competitive advantage.