Found it here:Where did you find the table? Have you got the link?
5k Run Times By Age And Ability - Running Level
5k running finish times by age for both men and women (good and average)
I wouldn't take it as gospel though, just a rough guide.
The best way is to go with the age grading based on the world record for that age group. Runners World have a calculator for anyone running, although most do parkrun and have this calculated for them.
Age-grading calculator for runners: How do your race times fare?
Whether you’re a younger runner or an older runner, working out the age-graded score of your recent race performances can be instructional, inspiring and just plain interesting
Their definitions are:
- 100% = world record
- 90% = world class
- 80% = national class
- 70% = regional class
- 60% = local class