alt Hacker News> I would also guess that sports betting sites like DraftKings or FanDuel would be even less efficient
Your strategy doesn't work on sportbooks to begin with, because bookmakers don't move the odds with the action.
That is, there is no such phenomenon as "the over is exciting therefore overpriced". Bookmakers price purely based on facts and statistics. Their pricing isn't affected by excitement nor by how many people are betting a certain way.
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>Bookmakers price purely based on facts and statistics. Their pricing isn't affected by excitement nor by how many people are betting a certain way.
If this were true, lines would never move unless there was breaking news, but we see lines move all the time without there being any material change to those "facts and statistics".
> Bookmakers price purely based on facts and statistics. Their pricing isn't affected by excitement nor by how many people are betting a certain way.
A bookmaker is a market maker, and they ideally want to end up with no net interest in a position. They then take guaranteed profit in the bid-ask spread, which in sportsbooks is the 'vig'. Bookmakers who adjust their odds in real-time don't have to be particularly clever about the fundamentals, just responsive to the competing demands on either side.
A bookmaker who intentionally takes a position on a game is the equivalent of a proprietary trader or hedge fund. It's potentially more profitable, but it's also adversarial against 'sharp' traders.
Bookmakers who set odds at the beginning and don't move with the action must set larger bid-ask spreads to compensate.