So 401k retirement funds started in 1978 so... does math ... they are only like 42~43 years old right?

So folks starting work and inventing in a 401k in their twenties should be somewhere around 60's... scratches head

So like, has there been any generation since 401(k)s became a thing has started retiring en mass yet? It seems like it hasn't happened yet (but I don't follow that stuff closely enough to know with any confidence.) But I imagine that when those folks with 401k's actually hit "retirement" age, something awful is going to happen.

Either the money they need to live off of won't be enough if they retire in between bubbles busting or worse when the value crashes during a bust right when they needed it the most.