Its totally anecdotal but of all my college friends, only one is left in SD. We all went to CSUSM. My best friend was born and raised in Escondido and just moved to SE Kansas. I admit thats a bit extreme, but on 40k no way was he going to have a kid and a wife that didn’t work.
Its not the young or the old that are making up the bulk of the people leaving. It’s those who have median(or less) household incomes and that are in danger. Its the dreaded Palm Spring scenario, which always leads to decay.
As to SF new York and Boston. Yes they have young professionals in droves but very few stay. I would bet far more stay in SD. Its a VERY transient place. You goto these places for a few years after college until the pressure cooker of career and low living standards forces you out.
