The Average Age Is 21, A Decade Ago It Was 18? No Answer To Impossible Trivia

You can win two pair of tickets to see the band Nickelback on Tuesday at the Wells Fargo Center in Philadelphia with the correct answer to this question on Friday... morning. No one could answer it Thursday morning.

The average age of people who do this is 21 years old.  A decade ago it was 18.  What is it?

Tell me at 7:20 a.m. Friday on the Lite Rock Morning Show.