The NBA’s Midseason Scoring Crackdown Also Made Games Less Predictable
The NBA’s Midseason Scoring Crackdown Also Made Games Less Predictable
Favorites are winning less since the league's new "officiating focus" came into play.
As a numbers enthusiast, I can’t overstate how cool it was to see my friend
break a true Stats Story™ this season, in uncovering what appears to be an honest-to-goodness midseason plot by the league to reduce scoring, call fewer fouls and… sorta not tell anybody about it (at least not publicly) and hope no one noticed.Luckily, Tom DID notice.
has a great summary of the whole affair here, alongside an interview with Tom that I would encourage everyone to read. It’s an amazing example of statistics helping to break a story before anyone in the traditional media caught wind of it — take that, Woj — and it’s something that should be taught in every data journalism class around the country.This story matters, too. With major pro leagues willingly partnering more and more with gambling companies in recent years, we’ve seen mounting questions about how to do that while maintaining the integrity of the on-field product and its outcomes.1 Midseason changes like the NBA instituted can have huge effects on things as fundamental as how many points get scored, who wins and loses, and how predictable all of that is.
We already saw this with the moving target of over-under point totals in the betting market at different moments in the season. In terms of scoring environments, there seem to have been three different “mini-seasons” in 2023-24: A moderate pre-December period that resembled the output from last year; a period between December and the All-Star Game in which all hell broke loose; and the sharp drop in scoring since the ASG that Tom documented.
All of this is well-known by now, including the fact that betting unders since the All-Star break would have made you a LOT of money if you knew about the NBA’s new “officiating focus” beforehand.
But what’s also striking is that games are becoming a lot less predictable under the new paradigm, too.
We can see this by looking at how often favorites (using my Elo ratings as a statistical measure) have won during each segment of the season, as well as using Brier Scores — the average squared difference between a pregame probability and what actually happened — to look at the degree to which predictions have been off.
During the early part of the season, favorites won 63% of the time, which is relatively low by recent standards. (Since 2009-10,2 favorites won around 66% of the time, even in early months of the season.) Between December and the All-Star break, as scoring was taking off, the win rate for favorites rose to 65%. But ever since, as scoring has dropped, favorites are now only winning 62.8% of the time.
By Brier Score, this has been the most unpredictable segment of the season as well. And while you might think the doldrums of the regular season are typically less predictable using a statistical system, since the best teams can sometimes coast before the playoffs, that hasn’t been the case. Looking back to 2009-10 once again, March has typically been the most predictable month on the NBA calendar in past seasons. In 2024, though? Not so much.
This makes some sense — lower-scoring games have more variance and make it easier for underdogs to win. When leaguewide scoring drops by 5 points per game — a magnitude of change that, for context, hasn’t happened between seasons since the end of the 1999 lockout — it’s going to potentially mess with the balance of the game and how often better teams win.
But that’s also the point. In a manner reminiscent of baseball’s juiced ball — and its sudden postseason disappearance — in 2019, the NBA has made its teams play under multiple different conditions this season, each containing their own metagame. Those changes came with little to no warning, and had huge effects for players, coaches and even the people whom the league has encouraged to bet on the games. In the past, maybe nobody would have noticed — but now, there are mechanisms to detect when leagues change things like this, and journalists like Tom to call them out for it.
Filed under: NBA
Players have been suspended for any hint of impropriety related to betting, for instance.
And excluding the COVID-altered seasons of 2019-20 and 2020-21.