5% is probably a good guess for people who choose to enter races. In the Philadelphia broad Street 10mi (probably biggest 10mi race) this year I just ran it steady at about 7:45/mi and that was at the 10% overall mark. Last year I ran it all out at 6:30/mi and that was 2% overall, 5% in the 25-29yo male group. Very few random people could run a single 7 minute mile though. Hell I couldn't in 8th grade gym class (7:20) and I was healthy just not a good runner at all