Basically, it assesses the quality of all shot attempts based on the expected eFG% from any spot on the floor when factoring distance from the rim and distance from the closest defender. It also factors time left on the shot clock. (Shot quality declines as you approach the end of the shot clocks because players become less judicious about passing up mediocre shots in the hopes of a slightly better one later.)
Among some of the interesting findings is that, as one would expect, individual players with higher usage take more difficult shots.
Also, those with high usage are typically better at making difficult shots, which is why their coaches allow them to take them:
The team data is interesting. Some teams, like Houston, do well on offense by creating good shots, even if they don't shoot all that well. Other teams, like the Clippers, may not create such great shots, but they're such good shot makers that things work anyhow. The Wizards rank 20th in shot quality. Their expected eFG% based on the quality of shot is 54.2%. Unfortunately, they're also quite bad at making shots - ranking 22nd in shot making and shooting 2.4% worse than expected based on quality of shots. The end result is that they rank 23rd in eFG%. I wish he posted the data from last year. I'd like to think that the Wizards actually have some pretty good shot makers and in a normal year would shoot above their expected eFG%. But maybe I'm wrong.
Defensively, the situation is completely different. The Wizards are the best team in the league at forcing opponents to shoot the wrong shots. You heard that right. Their expected opponent eFG% of 53.2%, which leads the league! But at the same time, the Wizards are a wild outlier in opponent shotmaking. Opponents are shooting an unbelievable 3% better then expected based on their shot quality. This is the worst "variance" in the league... by a lot. The next "unluckiest" team are the Pistons whose opponents shoot 1.8% better than expected. After that, nobody else has worse variance than 0.6%. Thanks to the Wizards' variance, they manage to post the worst eFG% in the league despite ostensibly allowing the least desirable shot profile!
It's notable that great defenses like Utah and LA post merely so-so opponent shot profiles but manage exceptional opponent eFG% thanks to massively negative "variance". Teams are shooting worse than they "should" based on their shot profile. So something else must be at play. Clearly, there is some other factor that is causing Wizards opponents to make shots at a better than expected rate (and Utah opponents to miss them at a worse than expected rate) that isn't captured by shot location, proximity of defender, and time remaining on the shot clock. Maybe the Wizards are allowing the wrong shooters to shoot. Or somehow they allow shooters to feel more comfortable even though the data says our defenders are still nearby. Maybe our opponents are allowed to step in to their shot instead of being off balance. Our lack of rim protection surely plays a role. Shooting a floater over a big man looks the same in a statistical shot chart, but it's harder to shoot over Rudy Gobert than Mo Wagner. But I suspect our problems exist out on the perimeter too. And they're not so easily explainable.
They have the 3rd best 3rd quarter defense!
