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1. ## Opening Lines

Getting boring around here with nothing but the same old arguments, so…let’s start a new lightning rod and talk about “openers”, maybe something useful will fall out of the cracks..

There are many people that use opening lines (outside of line moves) as part of their handicapping. From very simple, i.e. in football the favorite is -2.5, therefore the books are looking for favorite money, to all kinds of line comparison between previous openers and other voodoo that usually makes no sense to me. There are people that swear by understanding the books’ “motives”, while others think that using the line as a variable in a model is counterintuitive as that line is one the thing you are trying to beat.

All the repetitive discussion on how everybody who builds a model is a retard and/or that the line makers have some special knowledge that can only be divined directly from the gods has me thinking. Let’s say in baseball you take all your basic stats that are easily scraped from the web (i.e. WHIP, ERA, W-L, Bullpen, ERA, Team Batting, home field advantage, etc., etc.) and stick them in a basic regression model you could probably get a pretty good opening line predictor. (Lord knows I’ve built some in the past). Now my guess is that most models that use basic regression from easily sourced data are lacking and will lose in the long run. The hard part is recognizing that the variance (i.e. picks) is probably a bad thing. If I have a simple model that predicts a line of -150 for the favorite and the Vegas line is -115 what is the likelihood of the simple model outperforming the model used by the book makers? (And yes I acknowledge that line makers take many things into account including public perception which could mean from a truly statistical perspective the simple model could be more accurate for certain games). I won’t go down the whole “fading your own model” rabbit hole, but I’m thinking of building a simple regression model as a reference point. In the above example if I liked the favorite I would be very hesitant to bet on it. If my “real” model liked the underdog, then I’d be more apt to wager on it.

At the end of the day we are really fighting over fractions of a percent. If you’ve done this long enough you know the pipe dreams of 68% winners isn’t going to happen. But the difference between 53% and 54% is actually huge. I realize we are all trying to quantify the known information with our picks, but is anyone using the “unknown” hidden information that the book makers are providing to filter picks or make decisions?. I do know some people that used a similar approach to somewhat successfully quantify inside information in pari-mutuel markets. Obviously it’s a whole different world in sports betting, so let the flaming begin, and let’s hear all the opening line voodoo you use in your handicapping!

2. The linemaker has inside knowledge of historical betting patterns. Some teams are "public" teams with a lot of supporters that will bet on "their" favorite without regard to the actual game matchup. The betting public likes exciting games and tend to bet over for scoring. This sort of knowledge allows the linemaker to shade the opening line to take advantage of these types of bettors.

I don't know if any of this is true or not.

SBR
Bash 2012
Attendee 8/17/2012

3. Definitely True. But to what degree I'm not sure. Doesn't mean you can't quantify that in your "opening line predicting" model.

4. I agree that if this sort of stuff goes on, it would be good to incorporate it in your modeling. I don't know how you would find out about it without being involved in the linemaking at a major bookmaker.
If you are going to beat your competing modelers then you need a few "secret ingredients" in your modeling that the other people don't use. Something like you're talking about here would provide you with an advantage over the competition.

SBR
Bash 2012
Attendee 8/17/2012

5. I have no idea why you would try to create a model to predict the model that sportsbooks use, when you can instead try to estimate the true odds of a team winning and profit from it. People make this harder than it needs to be.

6. Originally Posted by evo34
I have no idea why you would try to create a model to predict the model that sportsbooks use, when you can instead try to estimate the true odds of a team winning and profit from it. People make this harder than it needs to be.
I don't think you actually read the post. I have a model that tries to estimate the true odds of a team winning. However my guess is my model doesn't take into account things the All Knowing Line Maker Model does. So the point of the post was to use a simple model that through curve smoothing should give a relative point to compare the line and your "true" model against. i.e. If you have two teams playing and the "True" model spits out;

Team A -150 win p = 60%

Vegas puts out the line as:
Team A -120 win p = 54.55%

Looks like a play on TEam A, NO?

So if you took all the basic stats and shoved them in the "simple model" and it spit out

Team A -185 win p = 64.91%

would you feel better or worse about your bet on Team A? Yes vegas has put out a line far from the model "this time", but the curve fitting for all the previous times the stats were similar came out much differently. Why? What is so different this time? For me if I know that everything points to Team A winning the every Tom Dick and Harry is likely using the exact same data, that would make me at least bet less on Team A today?

7. Originally Posted by cyberbabble
The linemaker has inside knowledge of historical betting patterns. Some teams are "public" teams with a lot of supporters that will bet on "their" favorite without regard to the actual game matchup. The betting public likes exciting games and tend to bet over for scoring. This sort of knowledge allows the linemaker to shade the opening line to take advantage of these types of bettors.

I don't know if any of this is true or not.
I don't think the supporters are the ones betting right after the opening of the line. The ones hitting refresh every 5 seconds waiting for the opening line to hit it in case there is value compared to what they think is a fair line, are usually quite sharp from what I understand. By the time the type of bettors you mentioned are even thinking to place a bet the lines are already shaped by the wise guys who hit for value. In other words the sharps are shaping the markets and I don't think the line maker would care too much about the square betting public when deciding on the opening line. I might be wrong though.

8. Originally Posted by allin1
The ones hitting refresh every 5 seconds waiting for the opening line to hit it in case there is value compared to what they think is a fair line, are usually quite sharp from what I understand
they might not be betting the right side but moving the line the other way cheaply, later hammering for more value

9. Price manipulation?....say it ain't so

10. Originally Posted by chunk
Price manipulation?....say it ain't so
it ain't so

i was theoritizing ... if there are people who refresh to get openers then its fair to assume that there are also people who refresh to get the first line movement and chase that?

if the conditions are right, maybe you could get a snowball rolling for 1-2 opening caps?

11. refresh all day to get those \$250 pinny openers

12. I haven't done any of this so I can't give anything specific.

It seems to me that comparing my models line with the opening line would provide some useful information.

The linemaker uses the same statistics that I am using. He maybe shades the line based on his knowledge and experience. This makes the open a relatively "pure" number. At this point, I don't have to worry about manipulation, sharps vs squares, efficient market theory, etc.

There might be information that I could get from comparing my line vs the open. For example, the linemaker knows that people overbet last years Super Bowl champ. He shades the line a half point or a point to take advantage of this. If the open on the champ is always a point or so more of a favorite on the champ than my model, maybe this is happening. It might not provide a bet but it would be useful to know about it.

I could look at the at cases where my line differs from the open and look for a pattern. I could look at the final results of my model in cases where my model agrees with the open and cases where it disagrees. Maybe mine performs better when it agrees with the opener.

It seems to me that if my model is as good as the linemaker at creating the open line, this would be an indication I have a pretty good model. It would give me more confidence in my model.

The linemaker has to post a line in every game. I don't have to play every game. I am starting from a good base with my model and can then try to look for specific bets.
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