My #1 hobby, pastime, or whatever you want to call it, is distance running. One thing that most of us learn as we get a bit older is that we slow down. Age-adjustment factors help us compare times of older runners (in this case, any runner over 30 years old) with "open class" runners.
The tables shown in these pages can also be used as "equivalent performance" tables for a runner of any age. The basic assumption of the equivalent performance tables is that world records at various distances are comparable, so any specific percentage of those world records is also comparable. Using this assumption, you can even compare men's and women's times, based on each person's percentage of a given world record.