Why lines move: Bears −3.5 → −3

Lesson 4 of 7 · 4 min read

You'll hear it on any NFL pregame show: "The Bears opened −3.5 and they're down to −3 by Friday." That one sentence holds most of what you need to know about how betting markets work.

First, which bet is that?

The −3.5 is the spread, not the moneyline. It's an easy mix-up, because people say "the line" for both. The spread is about margin: Bears −3.5 must win by 4 or more. The moneyline is a separate price on who wins outright, like Bears −180. When analysts talk about a team going from 3.5 to 3, they almost always mean the spread.

Where the first number comes from

The first price posted is the opening line, or opener. For the NFL, most books post next week's openers on Sunday night, right after that week's games, not on Tuesday (some even hang early look-ahead lines a week before). A few respected books open first, often at low limits, and professional bettors test those numbers straight away. Much of the early correction happens before Monday morning, and other books largely follow.

What moves a line

Between the opener and kickoff, lines move for two reasons:

• News. An injury report, a quarterback ruled out, a windy forecast. The game itself changed, so the fair number changed.
• Money. Books move away from the side taking bets they respect. One professional's bet can move a number more than thousands of small ones: that's the difference between sharp money and square money.

Bears −3.5 to −3 means the market now rates the game a little closer: maybe a Bears starter is questionable, or bettors the books respect took the Lions. If you took Lions +3.5 on Monday, you beat Friday's +3. If you like the Bears, waiting got you the better number. Neither tells you who wins. The last price before kickoff is the closing line, the best-informed price the market produces.

Why that half-point is a big deal

Football scoring comes in 3s and 7s, so some winning margins happen far more often than others. These are key numbers, and in the NFL the biggest are 3 and 7. In the margin table Consensus Edge's spread model uses, about 1 in 7 NFL games ends with one team winning by exactly 3.

That's why −3.5 and −3 are very different bets. If the Bears win by exactly 3, a −3.5 bet loses and a −3 bet is a push: your stake comes back. The half-point, called the hook, is worth the chance the game lands exactly on the number it crosses. Across 3 that's a lot; across most other numbers, like 8 to 8.5, it's far less. Books know this, so around 3 they often change the price before the number: Bears −3 at −120 is a different bet from Bears −3 at −110.

Consensus Edge keeps re-pricing

A price is only good at the moment you can bet it. Consensus Edge rebuilds the board about every 10 to 20 minutes, right up to kickoff, so line moves and late news show up in its numbers. Once a game starts it stops pricing it and freezes the card at its last pregame numbers, marked In Play.

Terms in this lesson

SpreadMoneylineOpening LineLine MovementSharp MoneySquare MoneyClosing LineKey NumbersHookPushIn Play