Comparison of WNBA and NBA 2-Point Field Goals

Comparisons of WNBA and NBA Association-wide, season-level data were compared in a previous post. For the season of each that was analyzed, disparities in FG% were evident. Initially, the NBA appeared to be more successful shooting, 44.9% to 42.5%. However, when excluding dunks, the WNBA was slightly but significantly more successful, 42.5% to ~40%. Having recently acquired WNBA play-by-play (PBP) data for the 2016 season, we can more granularly analyze FG%.

All WNBA data were extracted from the regular season 2016 PBP which is available upon request. I will dump this data along with the regular season PBP data from the 2014 and 2015 seasons in a future post. The NBA shot type and assisted shot type data for the 2015-16 season was culled from Basketball Reference.

Table 1a. WNBA & NBA 2016 counts

Type	Total	NBA	WNBA
All 2FG	Made	75549	9815
	Attempted	153768	20676
Shots	Made	35680	4769
	Attempted	89487	12318
Layups	Made	30439	5045
	Attempted	53920	8356
Dunks	Made	9430	1
	Attempted	10361	2

Table 1a contains counts and 1b proportions of 2FGAs segmented by shots, dunks, and layups between the Associations for the regular seasons ending in 2016. The class of ‘shots’ includes not only jump shots but also others identified in the PBP as floaters, hooks, and runners. Table 1b also contains Chi-square test-statistics demonstrating that the is NBA is slightly more successful shooting 2-point shots. The WNBA is significantly more successful with layups. The Chi-square was not performed for dunks because only 2 were attempted by WNBA players.

Table 1b. 2pt-FG% by Shot Types

Type	NBA	WNBA	χ²	p
All	0.491	0.475	6.961	0.008
Shots	0.399	0.387	2.623	0.105
Layups	0.565	0.604	12.230	0.000
Dunks	0.910	0.500

So, these findings provide a more nuanced perspective on the findings from the previous post that WNBA is more successful shooting non-dunk shots. The two posts did employ data from different seasons. Nonetheless, given the present data, the two Associations ostensibly shoot 2-point shots (i.e., not dunks and layups) with similar successfulness—the p¬¬-value approaching conventional significance levels is likely a result of large quantities. That is, a 1 percentage-point advantage to the NBA may approach significance statistically, but I suspect it is ecologically meaningless.

Alternatively, the WNBA was significantly more successful than the NBA shooting layups. My initial notional hypothesis was that because males are predisposed to heightened athleticism, there are more contested or blocked layup attempts in the NBA. Ironically (to the impetus for pursuing this line of research), although blocked layup attempts can be extracted from the WNBA PBP, I am unable to locate blocked layup attempt data for the NBA (short of scraping). Likewise, contested shots attempted from with ≤5ft from the basket are available for the NBA but shot contesting is not recorded in the WNBA PBP.

Table 2. Assists on Dunks + Layups

Dunk + Layups	NBA	WNBA	χ²	p
Made & Assisted	15536	2749	6.596	0.010
Made	64281	8358
Proportion Assisted	0.242	0.329

Table 2 contains the proportion of dunks and layups, combined, that were assisted. The WNBA assists on significantly more of their successful layups (and dunks) than does the NBA. So, this might also explain why WNBA players are more successful executing layups. Because the WNBA assists on a greater proportion of layups, there may be more floor spacing or player movement such that defenders are less frequently positioned to defend layup attempts. Indeed, this notion is interrelated to there being greater athleticism in the NBA, as well as greater size, and thus less floor space in the NBA. Lastly, WNBA players may execute successful layups in certain scenarios whereas NBA players would likely execute successful dunks such as on uncontested fast breaks.

If athleticism were the sole determinant in explaining WNBA layup FG% superiority, there would be little recourse for defensive strategists other than playing larger or quicker players. However, if it is the result of floor spacing or player movement, I suspect WNBA coaches transiently employ zone defenses to narrow passing and driving lanes to reduce opponents’ layup success.

Summarily, this report indicates that WNBA and NBA players shoot with similar accuracy on 2-point FGs that are not dunks or layups. Also, the WNBA is more successful on layups than the NBA. This author posited three reasons why this may be: (a) greater athleticism and size on NBA players results in more contested layup attempts and passes; (b) relatedly, the WNBA assists on a higher proportion of its layups which may be the result of more floor space or player movement, but is also related to point (a); and, (c) NBA players may execute dunks in many scenarios where most WNBA players would have to execute layups, also related to point (a).