For more colour, see this article, which shows the same trend on the same timelines for a bunch of other distances—steady progress till 1940ish, a 10-15 year WW2 gap, then further steady progress mid 1950s on.https://www.scienceofrunning.com/2017/05/the-roger-bannister-effect-the-myth-of-the-psychological-breakthrough.html?v=47e5dceea252
For more colour, see this article, which shows the same trend on the same timelines for a bunch of other distances—steady progress till 1940ish, a 10-15 year WW2 gap, then further steady progress mid 1950s on.
https://www.scienceofrunning.com/2017/05/the-roger-bannister-effect-the-myth-of-the-psychological-breakthrough.html?v=47e5dceea252