The gap between men and women in track and field isn't as large as I thought..

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Based on the Olympics, for the 100m:
Men are around 9.6s
Women are around 10.6s
It's surprising that the gap between men and women is only about 10%
Even looking at long-distance running:
Men's marathon world record: 1:59:30
Women's marathon world record: 2:09:56
An 8% difference
Track and field must ultimately be a contest of physical strength,
so I wonder why the difference is only this much.