Are there any books or verified sources on this? It makes sense, but I always assumed they just balanced the money by sliding the line, and took the vig.
The total Vegas handle on most games can be found, and it is often quite different than 50/50.
For example, close to 80% of the public money was on UConn to roll Arkansas in the sweet 16 last year. That's one that Vegas got way wrong, which was beautiful.
Let's say you are running a sports book. If your goal is to have a 50/50 spread on each game so that you can just earn the vig risk-free, then you have two problems:
1. Ensuring a 50/50 handle is not as easy as it sounds. There is a lot of guesswork in that, and if you get it wrong you are exposed to a potential loss. And once you have that exposure, then you need capital to back it up.
2. The vig alone is simply not enough profit for the sports books. Since they are putting capital at risk (because of 1.) then they want to earn a hell of a lot more profit than just the vig.
All the sports books' research and analytics are
not for the purpose of setting a line with a 50/50 handle. Rather, it is for predicting a range of outcomes for the game--something like a mean result with a variance in either direction. The book then tries to set the line to entice the public to bet on the losing side of that range.
They don't get it right every time, but they do often enough to make a nice return on the risk they are taking.
I think stuff like Ken Pom is a great help to bettors, and is reducing a lot of the information advantage that the books have always enjoyed. But the bettor has to use that information correctly.
Edit: As far as "sliding the line":
Yes, the books do that if they misjudged the public and they have too big a position on one side of the bet. But they are not necessarily trying to slide their position back to 50/50.
And there are limits to how much and how fast they can move the line, because they might create "middles" that can be exploited.