[lasker]

If you believe that, why not just blindly bet whatever team the market moved against? If the line is Team A -10 / Team B +10, and then moves to Team A -12 / Team B +12, you'd be getting two free points on Team B, since the line move provides no indication of the actual probability, right?

exactly. WendysRox, if you truly believe all this rubbish, you'll have no reason not to follow jgilmartin's suggestion. I guarantee that your theory will be refuted very quickly.

[That Foreign Guy]

Let me propose you this: Bookie has NYG -3 @ NYJ. Bookie gets $500,000 worth of bets on NYG and $100,000 on NYJ. What do they do? They move the line down to -2 in hopes of getting more equal action.

If the bookie gets a ton of money on NYG -3 surely they would move to NYG -4?

Or they move it to NYG -3 -120 NYJ+100. Or they leave the line where it is and hedge their position with a different bookie / exchange, or they leave the position naked and trust that their line setting is better than the public's opinion. If they do move the line it's because the money is persuading them that their estimate was inaccurate.

Does this mean that NYG -2 is closer to what may actually occur? HECK NO! It means that THE PUBLIC PERCEIVES THIS TO BE closer to what may actually occur! That's it! It does not have ANYTHING to do with the probability of that event occurring!

Ignoring your wrong direction line move, you believe what the public percieves has nothing to do with actual probability? You're the only genius in a world of idiots?

Your point of view, to me, is like taking a coin flip and saying that because 60% of the public are on heads and 40% are on tails, then heads is more likely to occur. IMO, the odds have nothing to with probability, only action. Lastly, unless something new develops, I think I've made my thoughts clear. I apologize for sounding a little frustrated, but that's what I am. Perhaps I just need someone to explain it to me better.

Sportsbetting is not like flipping a coin. If you can't see why the public's opinion on a sporting event is significantly different from their opinion on a coinflip or a roulette wheel or whatever then that explains why you are frustrated.

I know not all line movements are equal but to say all are irrelevant is probably a worse fallacy than saying all are relevant.

[WendysRox]

yeah, I discussed this topic until I was blue in the face yesterday. eventually Justin7 made the executive decision that it was not worthy of the almighty think tank.

#1 Yes, I screwed up the line movement. Sorry.

#2 in a nutshell, it is simply outlandish to me to see so many people believe that because a line moves, the probabilities are more precise. IMHO, the line moves because of money, it's as simple as that. And, money moves because of perception of the bettors. If I am not a better handicapper than 80% of the public, then I am wasting my time. This may be where we start to disagree. I never, ever, ever include public perception into my bets. (*see footnote) You guys seem to bet solely based on line movement because you believe it somehow reflects actual probability. IMHO, too much math and not enough common sense.

* In a way, I ALWAYS use the public perception because I am constantly looking for a game where the public believes team A wins by 3 and my database thinks Team A loses by 1, for example. I am constantly searching for that game where public perception has driven a line away from what I believe to be it's true probability. I guess you could phrase this as "me against the public" and I believe that I can more precisely determine actual probability than them.

[CrimsonQueen]

I think both schools of thought are correct. Yes lines move based on public perception...but yes lines balance out based on actual probabilities.
Obviously neither side is always correct (perception/reality) but I'd say both come into play.

[That Foreign Guy]

I'm a worse handicapper than 80% of bookies so I tend to view their lines as mostly efficient and that most line moves make a line more efficient.

I think the big difference is that I don't believe large bookies are trying to balance their books on all but the largest events. All the traders I know win and lose on almost every event. They're basically doing what we do - try to get the probability as accurate as possible and get their money in with an edge. The difference is they get to set the price while we get to set the volume (including 0).