It's based on self-reporting - which has its problems, but certainly no more than personal observation.
And the issue is not whether one has trouble moving up any kind of ladder one wants to but whether one chooses to do so; the best available evidence says most don't so choose.
Not buying it, sorry. Do you personally know any stoners? Even if it’s your no good son-in-law living in a basement, do you know any personally? Or do you just know “of them”? Not trying to convince you of anything, just curious where your opinions come from.