"It's not too surprising to me. There are a lot of careers where 15 years experience is worth a lot more than 5 years experience. But there's not a whole lot of careers where 30 years experience is worth a lot more than 20. So you're basically going to hit the top of your field around age 40ish, after which your only options for significant income increases would be to change careers entirely (go into management) or make some other kind of drastic change that most people are too risk averse to make at that age (when they'll typically have a house, family, etc)" - Eric P