These opportunities exist because each book sets its odds independently. Sports books respond to new information asynchronously and the books’ different models can overweight the likelihood of certain outcomes and underweight the likelihood of others. From my experience, BetMGM and Fanduel often give favorable odds on favorites (short odds), and DraftKings, FoxBet, Barstool, and Twinspires give favorable odds on longshots.
Another reason these arbitrage and +EV betting opportunities exist is that US sports books are new, and the operators are prioritizing growth/debugging/marketing above the accuracy of their betting lines. Offshore sports books’ odds are far more similar to one another than US sports books’. I would predict that by 2025, the opportunity to make >5% +EV bets on US sports books will be a shadow of what it currently is.
These opportunities aren’t being taken advantage of for the same reason that blackjack players aren’t all card counters: It’s stressful to bet large amounts of money on high-variance events even when you know you’re a mathematical favorite. And once a casino is sure you’re a winning player, you’re no longer welcome to play.
For anyone with the stomach and the bankroll for making hundreds of these slightly profitable bets per week, the opportunity is incredible until you get limited. With 60% confidence, I would estimate that someone with a liquid bankroll of $100,000 could profit between $40,000 and $200,000 within four months of advantage sports betting (8-12 hours/week). All they would need to do is bet on all >2% +EV betting opportunities that OddsJam suggests (with a tight market width/confidence interval), and use OddsJam’s Kelly Criterion calculator to responsibly size their bets.
I would recommend that anyone considering this path be selective about suspicious-looking bets. Player props and alternate lines can be red flags for books to limit you quicker. If I lived in a state with legalized online sports betting I would 100% be pursuing this; I’m happy to answer more questions or set up a Zoom meeting via Calendly if anyone is interested!