Why do spreads increase or decrease in the days leading up to the game?

Question

Why do spreads increase or decrease in the days leading up to the game? For example, one game "Open" 16 and "Today" 5. What happened to make that go so far down?

Answer 1

To some extent, it's based on changing status of teams (injury updates mostly). But, it's mostly because of the way the public is betting.

Let's say the Pats are playing the Jets and the opening line is Pats -7 (whatever points the Pats get minus 7 will still beat the Jets). And, the betting public goes "Whoa, I think the Pats are going to win by at least 10 points" and put all of their bets down on the Pats.

At that point, if the Pats win by more than 7 points, the casinos are out a whole bunch of money (if they win by exactly 7, it's a push and the bettors get their money back).

So, the casinos raise the point spread to 11 points. Now the bettors are thinking "I still think the Pats are only going to win by 10 points. I'll take that 11-point spread" and they start betting on the Jets to cover the spread.

Now, when the Pats win by 24 points (38 to 14), the casinos still have to pay all of those people who took the Pats less the points. But, they also make money on all of those people who took the Jets and the increased points.

Answer 2

That means people are favoring one side way to much and the ligns are going out and trying to make the betting even. The more drastic the betting is towards one side means they are going to try and do what they can to even out the betting

Answer 3

Because the bets change in Vegas, and the odds makers fine tune the odds (I believe).

Answer 4

Possibly new info, but most likely heavy betting on the other side.