Originally Posted by
Wheell
This is the finest thread I have ever read at SBR or any other forum and I'm guessing it has been read by fewer than 30 people and understood by fewer than 15.
Some notes:
Ganch has a different background than most of the rest of us and he is understandably cautious regarding systems that have done all of their testing in sample and have been good in predicting the past. His point about sabermatricians not having designed their work for gambling markets is quite apt, particularly given that the market is itself aware of many of the advancements made by the sabermatricians.
I should add that the only betting lines worth discussing are the betting lines that the observer wishes to attack. For some of us only Matchbook and Pinnacle matter due to being limit capped at every other location. For others, 1 unit is $50 at Bodog. Designing a system to beat the market you are attacking is goal #1 and for some of us that is simpler than for others.
Long term market inefficiencies are obviously sustained by some facet of human or mathematical nature. There is one sport I can think of where if you bet the under on the middle 80% of over-unders (ignoring all but the highest 10% and lowest 10%) you would turn a small but steady profit for every year that wagering data exists. This inefficiency appears to me to be the result of human nature simply not understanding the nature of the sport and being unable to reconcile there vision of the game and the actual result. Or maybe people just don't enjoy betting on the under in the sport I am thinking of. Whatever the case may be broad market inefficiencies can persist unless corrected by a specific agent.
The book "Super Crunchers" discusses an air travel site that not only makes predictions but that also makes predictions about the quality of their predictions. With enough data you can become extremely confident in your aggregate success rate, particularly if you are constantly updating your database and digesting the new data.
As for books creating sharper lines, I can say with certainty that the lines are sharper than they were as recently as 5 years ago, and I can point to the factors why. As a general rule, sharp lines refers to lines that are more accurately predictive of the underlying reality. This doesn't mean the lines are unbeatable or that a 3 point favorite will rarely win by more than 20.
Past performance is not a guarantor of success, but if you are familiar with statistics, it can be a pretty good guide for how you should act in the future, and that more than anything else is what we are looking for.