This sounds dramatic and dire but I feel like the reason for the statistic is that by the 20 year mark in someone's career, if they're working for a big corpora

This sounds dramatic and dire but I feel like the reason for the statistic is that by the 20 year mark in someone's career, if they're working for a big corporation, they've likely been promoted to management if they have any social skills at all. Not because they can't program anymore, but because corporations try to promote people to management if they've been around a while and haven't screwed up, and they tend to pay them more if they accept.