Matthew Walker on health: what the evidence says · JRE #1109
“There was a 70% reduction in car crashes the following year when they made that sentence 0% something to to be a revolution. Here's a simple biological factor sleep that will drop accident rates by 70%.”
What the evidence says
Walker's 70% figure matches the real, reported result for the specific case he names: Jackson Hole High School in Teton County, Wyoming, which delayed its start time from 7:35 a.m. to 8:55 a.m. Teen driver crashes in the district fell from 23 to 7 in the year after the change, a 70% reduction, per the Teton County School District #1 board report on the change, using Wyoming Department of Transportation crash data for 16-18 year old drivers. A peer-reviewed 2020 Journal of Clinical Sleep Medicine study on a separate district's start-time delay (Fairfax County, VA) cites this same range as background, noting that 'several studies have found reductions in crash rates as high as 65% to 70% in several communities' following school start-time changes, while cautioning that effects vary widely across districts (from roughly a 6% decrease to a slight increase elsewhere). So the 70% figure is a genuine, sourced number for the specific district Walker cites, though it is on the high end of a range that is not consistent across every community that has tried this policy change.