Photo: USA Today Sports

Gambling on the NFL is big business, especially after a 2018 Supreme Court decision striking down a federal ban on sports betting. Recent estimates suggest that as many as 46.6 million people will place a bet on the NFL this year, representing nearly one out of every five Americans of legal gambling age. As a result, there's been an explosion in sports betting content, most of which promises to make you a more profitable bettor. Given that backdrop, it can be hard to know who to trust.

Fortunately, you can trust me when I promise that I'm not going to make you a more profitable sports bettor. And neither will any of those other columns. It's essentially impossible for any written column to do so for a number of reasons I'll detail shortly. (I'm not saying it's impossible to be profitable betting on the NFL, just that it's impossible to get there thanks to a weekly picks column.)

This column's animating philosophy is not to make betting more profitable but to make betting more entertaining. And maybe along the way, we can make it a bit less unprofitable in the process, discussing how to find bets where the house's edge is smaller, how to manage your bankroll, and how to dramatically increase your return on investment in any family or office pick pools (because Dave in HR and Sarah in accounting are much softer marks than Caesar's and MGM).

If that sounds interesting to you, feel free to join me as we discuss the weekly Odds and Ends.

Checking In On the Unders

In Week 7, I noted that unders had been hugely profitable so far this season and discussed structural reasons why unders tend to outperform overs (though usually not by enough to beat the vig). I also said I'd track the performance of the unders going forward to see if we could be profitable merely by mass-betting them every week. (My hypothesis was that unders would win somewhere from 50-52% of the time going forward.)

Week 9 was a phenomenal week as the unders went 10-3-1, giving a 43% return if you bet equal amounts on all games at -110 odds. Overall, unders have gone 25-16-2 since we started tracking; if you bet an equal amount on every game (and all action was at -110), you would have turned a 15.6% profit. At $10 per bet, your total profit to date would be $67.27. If you'd instead started with $160 and invested an equal percentage in every bet every week (rolling over your winnings or losses), you'd be up $82.16, or 51% of your starting bankroll.

Let's Talk About Those Lines

Every week in this space, I provide a table of "lines I'm seeing". I've discussed in the past how useless this is in practice for a picks column; Vegas can shade the odds on a given line to make it a better or worse bet than the spread itself would suggest, and if they cared about me (they certainly don't), they could even change lines in response to any inefficiencies I wrote about so by the time you read this column that inefficiency would be gone.

There's another way those lines are misleading, though; it acts like they're a monolith.

I get all of the lines I post here from nflgamedata.com, run by a guy named Lee Sharpe. I use that site because, while many sites want to keep their data in their own little silo, Lee is an open data evangelist; it's not just possible to scrape data from his pages, it's actively encouraged, and he goes out of his way to make sure everything keeps working. For someone like me who is working with NFL lines on a weekly basis, that's a massive boon. He even keeps a csv file of all of his data that anyone is free to access at any time.

Lee doesn't set the lines himself; he mostly gets them from Pinnacle sportsbook, but in cases where Pinnacle doesn't offer odds for a particular game, he'll find them from somewhere else. (As an aside, Lee gathers these lines for a "Confidence Pool" game he runs where participants assign confidence levels to specific game outcomes and see if they can outperform the Las Vegas lines. At the moment, just 21 out of 745 users are ahead of Vegas. Vegas is very, very difficult to beat.)

But different books will have different lines. One book might have a team at -3 while the other has them at -3.5. Even if two books both have a team at -3.5, maybe one is giving -105 odds on it while the other is giving +105 (meaning a win pays out more money on the latter book than the former). Lines and odds don't vary a ton from one book to the next (if they did, algorithmic betters could place contradictory bets on opposing sites with the most favorable odds for each side and book a small but guaranteed profit). But these small variations are often the difference between a 52% bet and a 53% bet, and that difference is often the margin between a profitable week and an unprofitable week, which is why serious gamblers engage in "line shopping", or hunting for the best deal they can possibly find.

This site illustrates the kinds of variance you can expect in lines. The "Line I'm Seeing" for the game tonight is Chicago -3.5 with an over/under of 38. But at the time I'm writing this, I could get anything from Chicago -3.5 (-110) to Chicago -3.5 (-105) to Chicago -3 (-120), and while most sites are offering an over/under of 38, it turns out I can get 38.5 on Fanduel at the moment if I'm willing to lay -115 instead of the standard -110.

(As I've mentioned before, the more of your money Vegas is willing to take on a bet, the sharper you should assume its odds are. That plays out here, too; these variances are much larger on bets with lower maximums. Totals and odds on player props, for instance, can differ quite substantially from one site to the next.)

What's more, books will often deliberately add "juicy" odds on a lower-limit bet in the hopes that once you're in the door, you'll make several other more profitable (for them) bets as well. But the end result is that a substantial percentage of gambling profitably is just constantly shopping around for the best odds you can buy.

For recreational gamblers like us, it's not as big of a deal; we're losing money in the long run, but hopefully, we're having fun doing it. But it might at least be worth keeping two or three different sportsbooks or betting apps handy and looking for the best odds you can find between them.

Lines I'm Seeing