The New York Times has reported that Nike's Zoom Vaporfly 4% and ZoomX Vaporfly Next% make their wearer 4 to 5 percent faster than the wearer of an average running shoe and 2 to 3 percent faster than the wearer of the next-fastest shoe. The newspaper has used new data to revise its statistical analysis from last summer. On the basis of the new dataset, comprising more than a million marathons and half-marathons since 2014, the advantage conferred by the Nike sneakers appears to be 3 to 4 percent greater than first reported. The International Association of Athletics Federations (IAAF) is investigating to determine whether that advantage is unfair. Its report is due next year. Brooks, Saucony, New Balance, Hoka One One and Asics either produce or plan to produce similar shoes. Eliud Kipchoge was wearing Nike Vaporflys in September when he became the first man ever to run a marathon – albeit an unofficial one – in less than two hours.