Line movement takes place on just about every wagered sporting event. When a game starts, the sportsbook closes the window on pre-match betting and opens the opportunity for live betting. Initial point spreads are frozen, and books must assess their bet volume at various odds offered before the event.
Deep Dive: Closing Line Value (CLV)
A deep dive into the myriad mechanics of sports betting uncovers the Closing Line Value (CLV). If the home team opened as a 4-point favorite and was bet up to -6.5 before the game started, the "closing line" is -6.5 points. Many bettors will have different numbers on the favorite, such as -4, -5.5, and -6, depending on when they bought in. Underdog bettors will also have different point spreads, like +4.5 and +5. If the team wins by double-digits, the line movement doesn't matter. It's when the final score falls around the closing line where a half-point can mean the difference between a winning and a losing ticket.
Behind the Lines
Oddsmakers move numbers based on the money pouring in. If a sportsbook gets $10,000 on the favorite at -7 (-110) and just $1,000 on the underdog at +7 (-110), the line could be adjusted to -7.5 (-110). The goal of the oddsmaker is not to predict the final score. It's to make a number good enough so that a similar amount of money comes in on both sides. They pay off the winners and hope to profit around +4.76%, which is based on the implied probability of opposing bets with -110 juice (110/210 = 52.38 per side, x 2 = 104.76, aka the bookie's over-round).
Market Call
Thousands of casual bettors are focused on the game, hoping they beat the point spread. However, a far smaller number of sharp, sophisticated bettors are focused on capturing the optimal closing line value. CLV is the value of a wager compared to the line when the betting market closes. If the opening line is -4 and you bet the favorite, then the line moves to -2, you've lost line value. Casual bettors pay little attention to line movement. A point or two might not seem like a big deal, but it is to serious bettors who are betting on sports. Getting an underdog early at +7.5 is significant if the closing line ends at +6. Another betting element is added - anticipating or predicting what opening lines are off and which direction they're likely to move. It adds up in your bankroll. Throughout a season, potential losses become pushes while pushes become wins.
Betting Strategy: The Long Game
If you can get a moneyline wager of even money (+100) and the closing line ends up -110, the betting market tells you that this wager has a 52% chance of winning. However, the odds that you locked in are 50%. That's a differential of +2% in your favor with the closing line value. Casual bettors wouldn't even notice, but sharp players do. Beating the closing line is how good sports bettors can turn a profit over the long haul.
Subtle Line Movement
Most line movement is subtle, varying by one or two points. Even a small edge in your favor can be significant, as not all betting numbers are equal in value. Key numbers in the NFL are 3, 7, and 10. Oddsmakers wouldn't be concerned with moving a favorite from 4.5 to 5.5, but a jump from 2.5 to 3.5 is enormous. The latter is leapfrogging a key number. At 2.5, it entices bettors to take the favorite, while 3.5 screams, "Grab the underdog at +3.5 before it moves back down to +3." If the sportsbook has too much money on the dog at +3.5 and too much on the favorite at -2.5, a 3-point victory by the favorite would be a significant loss. Oddsmakers want to avoid getting middled like that. Sportsbooks are actuaries assessing risks: they count their numbers - and their pennies - with great care.
Dramatic Line Movement
While subtle line movement is so common that it can slip under the radar, everyone takes note of dramatic line movement. When injuries are announced to a starting quarterback, an ace pitcher, a hockey team's best offensive player, or a basketball star, oddsmakers must shift the line fast, often by a lot. This is where keeping up with the latest information is vital. A minor, nagging injury in practice can quickly turn into something more serious. A key player sitting out one game isn't a big deal for a sports team. We've entered an NBA era where coaches will rest one or even two star players on back-to-back nights. They're focused on reducing key players' wear and tear to prepare them better for a long playoff run. But for bettors and oddsmakers, it's a big deal on that January or February night when the coach decides to bench a couple of his best players. The line can shift from -7 to -2, by four points in the NFL if a starting quarterback can't play, or a baseball team can go from a favorite to an underdog if an ace starter is bumped. Bettors can pick up tremendous closing line value if they are ahead of the curve.
Follow the Early Money
Getting a jump on which way odds are likely to shift goes a long way to maximizing closing line value. You don't need tarot cards or a crystal ball. Instead, utilize several areas to anticipate which direction numbers should move. Football odds are posted about one week before the games are played. Early bettors are wise guys who will wager far more money than the average player. When sharp money comes in one side, oddsmakers will make adjustments quickly. Number one, they want to get balanced action, so having too much money early on one side means they need to attract money on the other side the rest of the week. Number two, oddsmakers are human. They don't always make the perfect number. Oddsmakers will not be stubborn, believing their number is best. They won't stick with their original number and hope the wise guys are wrong to collect a huge payday. That's not their job. That would be gambling, and it's too risky. Their job is to limit risk by taking balanced action and being satisfied with collecting a 3-5% payday. Oddsmakers are flexible enough to recognize that they made a number that is a few points off and will adjust.
Predictive Factors
There are other predictive factors handicappers can examine to gauge which way numbers will move. For outdoor sporting events, the weather can influence a contest. It can be subtle, such as wind conditions for a baseball game or a rainy drizzle that could negate a big passing day from a football team with a star quarterback or great wide receivers. It could also be a significant weather event, such as 35 MPH winds or heavy snow. Those factors can move totals quite a bit. Savvy handicappers can lock in an early football total at UNDER 48 points, for instance, knowing that a blizzard or heavy rains are possible that will move the total down to 44. Injuries are another factor. If a quarterback played in Week 1 but took a lot of hits and was limping late in the game, that increases the chances he's not 100% for Week 2. If that team has a below-average backup QB, the nagging injury may play a significant role in line movement. The NBA and NHL play 82 regular-season games. Minor injuries often happen to key players who might be forced to sit or limit their minutes or effectiveness in upcoming games.
Numbers to Call Your Own
Power ratings are another factor in predicting betting odds. Power ratings are numbers assigned to teams that gauge their overall strength against other teams. By utilizing existing rankings or creating your own, a handicapper can come up with a number and compare that to the actual odds. Deviations will occur with the differential unveiling line value. If your data is accurate, it can help predict how the number will shift.
Line movement can occur at any time during the day or week, depending on how the money comes in. Serious handicappers always seek to identify predictive factors that explain subtle and dramatic line movement. Consistently winning sports bettors play the long game by collecting enough data to anticipate shifts in odds to maximize optimal closing line value.
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