Even in case you’re not a hard-core fan of the Ladies’s Nationwide Basketball Affiliation, you could have heard of the Caitlin Clark Impact. The speculation is that Caitlin Clark, the primary choose within the 2024 WNBA draft by the Indiana Fever, is the reason for the unprecedented improve in league attendance, attributable to her extraordinary expertise and charisma.
This scatterplot exhibits the typical attendance per sport throughout the 2023 and 2024 seasons for the 12 groups within the WNBA. The plot exhibits that total attendance at WNBA video games elevated by 48% from 2023 to 2024, with many of the groups seeing 16% to 68% extra followers.
The Indiana Fever have been a MAJOR outlier to this development, nonetheless. They’d a 319% improve in attendance from 2023 to 2024, which is why the crew’s attendance plots within the higher left nook of the graph distant from the remainder of the groups. They went from the low finish of crew attendance in 2023 to the very best in 2024.
The impact is much more spectacular contemplating the complete historical past of league attendance at over 6,000 video games from 1997 to 2025. Attendance had dropped from about 10,000 attendees per sport earlier than 2000 to about 6,000 simply earlier than Clark was drafted. That’s a lack of about 160 attendees per league sport averaged over 24 seasons. It doesn’t sound like a lot, however it provides up. It’s like a gradual oil leak out of your automotive. You retain seeing a couple of drops of oil on the storage flooring and earlier than lengthy, your check-engine mild comes on. After Caitlin Clark was drafted, common attendance elevated by 5,000 attendees per sport by 2025. That’s what’s referred to as Caitlin Clark Impact, however is she the reason for it?
One extensively cited set of standards used to judge causality was described in 1965 by Austin Bradford Hill, a British medical statistician. His 9 standards are
- Power. A relationship is extra prone to be causal if the correlation coefficient is giant and statistically important.
- Specificity. A relationship is extra prone to be causal if there isn’t a different possible clarification.
- Temporality. A relationship is extra prone to be causal if the impact all the time happens after the trigger.
- Gradient. A relationship is extra prone to be causal if a higher publicity to the suspected trigger results in a higher impact.
- Plausibility. A relationship is extra prone to be causal if there’s a believable mechanism linking the trigger and the impact.
- Coherence. A relationship is extra prone to be causal whether it is appropriate with associated information and theories.
- Analogy. A relationship is extra prone to be causal if there are confirmed relationships between related causes and results.
- Consistency. A relationship is extra prone to be causal if it may be replicated.
- Experiment. A relationship is extra prone to be causal if it may be verified experimentally.
Hill’s standards have been established for experimental research. For observational research, the Consistency and Experiment standards don’t apply.
Proof that Caitlin Clark is the reason for the nice will increase in WNBA attendance contains:
- Temporality is supported by the nice will increase in common sport attendance, as proven within the graphs.
- Gradient is supported by the continued and elevated attendance even after her rookie WNBA season.
- Coherence is supported by related will increase in merchandise gross sales for Clark and different gamers within the WNBA.
- Analogy is supported by related will increase in attendance for different notable gamers in sports activities, like Michael Jordan, Pelé, Walter Payton, Tiger Woods, Wayne Gretzky, and lots of others.
- Specificity is supported by her crew, the Indiana Fever, having by far the biggest improve in attendance regardless of the introduction of recent gamers to different groups from the 2024 draft.
- Plausibility is supported by the nice curiosity Clark drew in faculty basketball at Iowa.
Paradoxically, the power of the correlation within the knowledge, the criterion most individuals affiliate with causality, isn’t an element. The truth is, it’s the reverse. Clark’s presence is an outlier to the development in historic attendance. So, whereas correlation doesn’t all the time indicate causation, causation doesn’t all the time indicate correlation.
Whereas no particular person criterion is foolproof, causality is extra convincing when a lot of Hill’s standards are met. But regardless of these observations, there are nonetheless individuals who don’t consider that Caitlin Clark is the reason for the rise in WNBA attendance. What do you suppose?
Learn extra about knowledge relationships and causation in Chapter 7 of Stats with Kittens.
