Ah, sorry poor wording. What I mean is that a developer's skill increases non-linearly with experience. That is, there is a sharp spike after only a few years of working in industry. I won't argue that skill doesn't continue to increase with experience, but I think the difference between my skill in 9 years may be proportionally lower than the skill difference now and in, say, 2 years. However, employers generally seem to work on linear experience models, so if I start at $80k now, in 2 years I may get a simple cost of living + (hand-wavy) 10% salary increase, whereas if your assertion is correct I should probably be getting paid closer to the controlling market salary of >$120k. Do you think the proper way to handle this is for new developers to quit after 2 years?

Oh, if that's what you're worried about, a) you're right, employers routinely exploit wage anchoring of employees already on the payroll, b) I don't know if I agree that devs slow down in growth after two years, and c) regardless of whether they do or not, quit and demand wages commensurate with the value you bring to the company.

I used to work for $30k prior to discovering that there exist better options. Now I try to be the little Internet fairy whispering to young devs "There are better options!" ;)