I feel as though there was a thread on this not that long ago. Intuitively, I've always thought it was the 3k, but when I look at it by how far ahead WR is to 2nd fastest person/10th fastest person, it appears to be the 2k.
%2nd/1st %10th/1st
800 100.20% 101.61%
1000 100.17% 101.76%
1500 100.17% 101.54%
mile 100.13% 101.89%
2000 101.09% 102.32%
3000 100.54% 101.54%
Steeple 100.00% 100.77%
5000 100.27% 101.51%
10000 100.33% 101.35%
marathon100.05% 100.97%