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Navigating WNBA.com’s new stats page: Why is scoring down?

Does it seem like WNBA games aren’t scoring as high as they did last season?

It isn’t just you. Scores are down, and teams’ offenses don’t seem to be shaking off that typical early-season rust.

It might be easy to blame the lack of star power. Maya Moore, of course, is taking the season off. Skylar Diggins-Smith just had her first child. Diana Taurasi, Sue Bird, Breanna Stewart and Angel McCoughtry have all been injured. That’s quite a bit of scoring prowess missing time.

There’s more to it than that, though. There are injuries and other absences every year, unfortunately, and the talent level in the WNBA should still be high enough to make such drop-offs minor.

So let’s break open our WNBA database and see if we can find another explanation, shall we?

Current scoring struggles

First, let’s take a look at what’s currently going on in the WNBA. Using the sortable team stats page, we can see that there are just two teams — Washington Mystics and Las Vegas Aces — averaging more than 80 points per game.

Of course, there’s a problem with that: It doesn’t account for pace or minutes. Offensive rating (points scored per 100 possessions) is preferable here, so we’ll be using that as a general gauge of offensive performance throughout this piece. By changing the general team stats page from “Traditional” to “Advanced” we can show offensive rating (OFFRTG) across the league:

Team stats sorted by OFFRTG (points scored per 100 possessions). Unsurprisingly, the Mystics have been head and shoulders ahead of every other team offensively.
WNBA.com

The mean OFFRTG in this set of data (which we’ll have to calculate manually, unfortunately) is roughly 97.03. In other words, WNBA teams are, on average, scoring 97.03 points per 100 possessions this season. We’ll use that to compare average team offense from 2019 to that of previous seasons.

Historical context

Before we do that, though, there’s one important thing to consider: The 2019 season is still just five weeks old. Offense typically improves throughout the course of a season (it’s difficult to establish chemistry early on when some of your players are still overseas, after all), so comparing our five-week 2019 sample to previous seasons in their entirety might throw a wrench in things.

To compensate for this, we’ll have to sort historical data into similar five-week samples. Let’s now look at 2018 team stats while using the “Advanced Filters” option to set a custom date range to the first five weeks of that season:

Organizing 2018 WNBA team stats by OFFRTG (points scored per 100 possessions) through the first five weeks of the season. Notice the filters used at the top.
WNBA.com

This data confirms that, yes, scoring is down from 2018. The mean OFFRTG from the first five weeks of the 2018 season is about 100.43 — almost 3.5 points per 100 possessions higher than at the five-week point in 2019.

Now, because we can, let’s do the same thing going back a few more seasons. All we need to do is keep changing the season at the top of the page and the custom date range we entered to keep things consistent with each season’s first five weeks. Manually calculated averages of OFFRTG values yield the following trend:

This is, obviously, a very bare-bones graph (we’re just looking through basketball stats here, not taking a masters-level Excel course!). But it shows that through the first five weeks of each season, WNBA offense has been trending downward for some time.

A two-season drop of six points scored per 100 possessions is not a small one. But the question is: Why? Are teams just shooting really poorly, or is it something else?

Finding a correlation

Well, let’s find out! Using the same advanced stats page and date filtering method, we can look at the average eFG% (effective field goal percentage — preferable to regular field goal percentage because it accounts for three-point shots being worth more than two-point shots) across the same time span to see how WNBA teams have been shooting the ball.

(Remember that the values shown in these graphs are averages that have been calculated manually!)

Okay, so league-wide eFG% is also down since 2018, which would explain the drop in offense. However, there’s almost no difference in eFG% from 2016 to 2018. League-wide OFFRTG was fluctuating during this time period, as shown by the first graph, so there must be other factors in play here besides shooting.

How about free throws? If we go back to “Traditional” stats and adjust for 100 possessions (important because we did this for points scored, also a “counting” statistic), we can see what free throw attempts looked like over the same time period:

AHHHH! Now that’s interesting! Free throw attempts and OFFRTG have had similar drops over the past three seasons.

Free throw rate — a more popular metric and one of the “Four Factors” that can be found using WNBA stats — yields a similar trend:

This means that so far in 2019, WNBA teams have on average attempted 0.234 free throws per field goal attempt. Through the first five weeks of 2018, they attempted 0.297 free throws per field goal attempt, and so on.

So what’s the conclusion?

It’s clear that WNBA officials are calling far fewer fouls in 2019 than they have in years past. While correlation does not equal causation, it’s not unreasonable to think that the lack of free throws has had an adverse effect on WNBA offenses. In particular, teams that rely on free throws for a bulk of their offense (Atlanta and Las Vegas come to mind) may be putting up worse-than-expected numbers because they simply aren’t getting the calls they once were.

To be fair, teams not named “Mystics” haven’t been shooting the ball very well, either. When you combine that with the lax officiating, you’re going to see some ugly offensive numbers. We’ll see if this trend continues throughout the season or if things regress back to where they were previously.