I do not believe there is any data to back up this assertion. Indeed, it's exactly this kind of discrimination that people are looking to combat.

Looking around my office there is a person here who's about a year younger than me but I don't think it's a given that this one year difference makes them somehow less experienced than myself. We're both adults in our forties with many years of experience each, quibbling over a year hear and there strikes me as pointless and counter productive. There are other, more important, differences between us.