Line moves are a big factor in sportsbetting, but why do they happend and what are the implications of a line-move? I would be greatful if some people with knowleagde of this subject could share.
(when I talk about line moves I do not nessescarly mean that the spread changes, just that the odds for a given spread changes)

My general assumptions as of now is that the current odds are the best odds availible to predict the outcome of the sportsevent.
For example, if the odds used to be 1,952/1,952 (=50%/50%) and 3 hours later becomes 1,87/2,05. Id would assume that the current odds 1,87/2,05 are correct and that the probability for the outcomes are 52,3%/47,7% before taking any other information into account.

Is this a good assumption or should one factor in the linemove?
If you evaluate the linemove, do you assume that the line move is partially unmotivated (which means that the probability should be closer to the earlier odds than what is calculated from the current odds), or do you assume that the line should have moved more than it did, and that the "true" probability is futher away from what is implicated by the original line than that which is implicated by the current line??

A related question is, if there has been a line move, do you expect it to continue? or would you assume that the future movement of the line is random? (before taking other information than the actual line move and its reason into account)

The line moves in reaction to the betting. The books want equal money on each side of the line. This insures they pull a profit from the juice. They do not want to gamble. There are some games where almost the entire public is on the same side. When the odds move dramatically in one way, you can be sure that most of the money is down on that.

The line is made with the intention of attracting equal betting on each side.

Silence is better than garbage.

Heh.

Oh, 2 acceptable sentences out of 7 isn't that bad.

I'll give 2 more as not vomit inducing.

Ooh, ooh, I want to play. We have 2 acceptable, 2 not vomit inducing, and 3 vomit inducing, right?

Acceptable.

Vomit inducing (common misinformation though, that you hear a lot).

Not vomit inducing (It's irrelevant, but it is technically true in the situations where the money ends up balanced).

Vomit inducing.

If we're claiming that only 3 of the 7 sentences are vomit inducing, then either this or the final line must be acceptable.

Acceptable because it would be true with a judicious addition of the word "sharp" in the appropriate spot.

I'm not buying the 2-2-3 ratio. I see 2-1-4.

The sad part is how much I wish all the vomit-inducing things were true.

Back to topic plz

Anyway, one approach to the problem that I have recently given more credit to is that "sharp money" moves the line on betexchanges like betfair. Basically, the thoery is that a/some huge player(s) (who is winning and has more information than the market) unloads on one side on say betfair. This will obviously move the line on said odds-exchange, and then the rest of the market (bookies) will follow.

Because the "sharp money" bets with some margin the implications are that if the line used to be 1,952/1,952 and moves to 1,87/2,05, you should think that the 1,87 has even higher true probability than what is implicated by the current odds.

The evidence I have to support this claim are:
1. Line-moves on betfair seem to be ahead of the rest of the market (bookies), and that the bookies then follows.

However, it could be argued that pinny is almost equally fast to change thier lines, (probably because thier automatic system and large action). So it could be argued that above is true only because the bookies are slow on changing thier odds.

2. Me and my brother have been placing some plays on bookies that offer higher odds than betfair latly(post-line move, bookie hasnt changed yet), and have thus been tracking the results.(Mostly soccer) The actual ROI has been alot higher than the ~~1-2% that would be expected from the betfair lines the moment we place the bets. (The ROI has been more like 5%+)

However, these statistics are based on only 200 plays or so.

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@unrealzeal: I think that "public money" is often overstressed. This may be a argument for betting dogs rather than favorites (as public likes favorites) but in context of line-move I do not think it matters so much.

The bookies want even action on both side, sure, but they can predict the public side even before the line is released so they may as well open it lower.

However, without any statistical support Id say that it feels like the dog odds often increases and the favorite odds decreases.(Esspecially in american sports) Please feel free to discuss this as well if anyone has some input on this.

As alluded to earlier in multiple posts, the books do not want equal money on both sides. Think about it - you're the book, and you know the fair line on the Notre Dame @ Michigan State line would be MSU -7.5. However, you also know that the public loves to bet on Notre Dame and thus you would get even money on both sides with a line of MSU -3. What line would you publish in this scenario?

If you make it -3, you get your even bets for your guaranteed little profit based on vig, but you're giving a ton of value to the sharp folks taking MSU -3, because you're giving them a free 4.5 points compared to the fair/true line. Wouldn't you rather take that hot value instead of giving it to the sharps? Of course you would - your business is maximizing profit, not completely avoiding short term risk. So you make it -6.5. 70% of the bets come in on Notre Dame which essentially puts you in the position of betting on MSU, except you're getting them at -6.5 instead of the fair -7.5, which is a significant advantage, plus you're getting +110 from all the clowns betting on Notre Dame, making your position better still. Sure, Notre Dame could beat the spread and you'd lose money, but there are 40 other games that day where you do the same basic thing, and there are 18 other weeks where you do the same thing, so you're going to get to the long run in a hurry.

The exception would be games where the volume is massively higher than normal such that if you lost on your position, you couldn't make it back by just offering a bunch more games. In this case you'd rather just take the balanced action, but it's the exception to the rule (Super bowl, BCS national title game, etc)

Oh boy. The books want equal money on both sides, but it never occurs. They therefore have to adjust the line to give themselves an advantage. That's why sportsbooks pay handicapping services to make the line for them. If you look very closely at the spread, you can often determine who the linesmaker thinks will cover.

It doesn't change the fact that the odds move in reaction to the betting.

This thread is taking a turn for the absurd.

Just want to say that this is not why sportsbooks pay. In LV it's mandated by law to have one, but that isn't to say that the books necessarily use LVSC's (for example) line. Often these lines are awful.

lines move all the time. often for little or no reason. most of the time it's impossible to predict and since i have no control over most movements i try not to be overly concerned with them. now if a line moves because of some new information about an injury, coach/player motivation, team collapse rates, turnover tendencies, etc. then i might take the move into consideration. the trick is being able to tell the no reason moves from the information moves.

What is the point of this law??? I thought books could make the lines whatever they wanted..after all they are`the ones whose money is at risk.
There is actually a law saying books have to use a line service and can't make their own..what in the world is the purpose of this law??

Actually a "line move" in soccer does not stem from Betfair usually, neither sharps betting there. If there's money influencing the market from somewhere, it's being placed at the Asian books in far larger amounts than possible at a time in Betfair. The market is developing there and not the other way around. Betfair or Pinnacle limits are way too small except for the very big leagues. Anything lower than the EPL, Bundesliga, La Liga, CL, etc. isn't interesting at the Exchanges for the big hitters.

Therefore, if you want to play the moves at slower books like it is done by the arbers, observe the Asians not Betfair.

There is always a reason for the move. It either moves because the public moves it by it's bets, or because of new information. IMHO, you have to handicap both the game and the line. Look closely at the opening spread and see which side the linesmaker is on. Remember that most of these guys are professional gamblers who watch games for a living. Don't underestimate how smart they are. Then handicap the game and determine if they are right or wrong.

You tell 'em.

Garbage > your first post > your last post.

Thanks for sharing

Hmm, are there any URLs where you can observe these asian odds in real-time?

Can anyone else confirm the above post?

"I bet some soccer ****, then was trying to find a score, and the attendance for the game was under 200"

-TomCowley

oh geez.

They can make their own lines but they must also subscribe to a line service. Seems odd but...

wat?

n/m i cant read.