Complicated thing to evaluate IMO. For one thing, lines often go up and down in the same week.
Typical pattern:
Line comes out Sunday night and promptly goes down a half point or a full point. Sometime around Monday the line flattens out, and if there is no significant news on the teams thru the week, it stays there for the most part. Sometime late Saturday or (usually) Sunday morning, the line moves the other way. What's going on? My take...the sharps hit the lines early, whereas the public bets late. I don't know too many casual bettors who place bets on Tuesdays or Wednesdays, much less a full 7 days before a game....almost all of them make up their minds around 11am or noon of gameday with very little thought or handicapping involved. But the serious guys will have a line in mind before it comes out, a week in advance, and are ready to pounce on anything that doesn't look right.
The books in many cases know which side the sharps will hit and which side the public will like (usually not the same side), and will set the line in such a manner that they'll get both sides hit somewhat equally***. They know the public is going to be all over (usually) the favorite, or the hot team, so they'll offer a slightly favorable dog line early, welcoming a little money on the opposite side to give them some balance. As long as the # isn't going to cross a key # like 3, 4 or 7 a little line movement isn't going to hurt them in most cases.
In recent years we've seen books more and more refuse to budge off the 3, instead adjusting the ML. Books still want equal action, but no way are they going to get middled to death anymore, dropping the 3's to 2?'s, only to end up going up to 3? later in the week, then getting slammed on the dog. This (moving off the 3) was actually somewhat common up until about 2-3 years ago, but obviously the books decided they could no longer expose themselves on such a key figure.
Then you've also got situations where sharps hit the
wrong side early, trying to move a line down, so they can come back with double the money on the opposite side (the side they really like) at a more favorable number later in the week. So the initial line movement may be a false indicator.
I've tried betting based on line movement and had no success whatsoever with it. But I've heard many people swear by it and say it works for them. I just think in a lot of cases you really don't know what these line movements mean because of the amounts of money and tactics the big syndicates are using. It's best, in my opinion, to just handicap the games.
(Probably a lot more info than you were looking for...sorry.
I think the whole topic of line movement though is extremely complicated and not that easily summed up)
***Comment on "equal money on both sides". I am sure someone will reply and say that books don't necessarily want equal money on both sides, that it's a myth, etc etc. This could be a whole 'nother topic unto itself. No, I don't believe the books want equal money
all the time on every game. There are certainly situations where they don't want this. But in general, they've got to keep the books balanced, or they put themselves in a position where
they are taking the gamble. Anyways...
