A little disclaimer before viewing the following results.
Obviously, the fighters we actually have birthdates are, for the most part, more "well known" than the fighters who we don't have birthdates for. So, in the following, you can't compare to a 50% win percentage (you can't anyway, because draws are included), you'll have to compare to the sample average. Having said that...
Win % by Age
In the above graph, the dotted line represents the sample average. I'm very surprised at the almost impeccable trend downward, which starts all the way at the beginning when the fighters are in their teens.
The teenage group boasts an astounding 79.8% win percentage. The spike after age 39 is undoubtedly a result of the few ageless wonders that we've seen in the recent years of MMA, carefully picking and choosing their spots rather than retiring.
Originally posted at: http://www.fightmatrix.com/2011/04/12/age-it%e2%80%99s-impact-on-fights-part-ii/