Using COVID-19 response policy to estimate open water and swim drafting effects in triathlon

This study investigates the causal effects of open-water swim drafting by leveraging a natural experimentinduced by staggered race starts during the COVID-19 pandemic. Before 2020, athletes started in groups,enabling drafting benefits, while pandemic-related restrictions significantly reduced these opportunities.Using agglomerative hierarchical clustering of swim-out times, I analyze optimal drafting positions andestimate their impact on Swim-Out performance. Our empirical findings reveal that swim drafting benefitswere statistically insignificant in 2020 but persisted post-pandemic at slightly reduced levels. I find thatdrafting becomes advantageous only from the third trailing position onward, with earlier positions primarilyserving to minimize fatigue. To mitigate endogeneity, I employ athlete and event fixed effects. The seeminglyinverse decaying nature of drafting benefits partially addresses some concerns of simultaneous reversecausality and omitted variable bias. This study provides the first largescale causal estimate of drafting effectsin real-world triathlon race settings.