I'm talking about improvement on a percentage basis, not absolute: even if your productivity is improving linearly at 1 awesomeness-point per year, your fractional improvement ("% awesomeness gain per year") is going to trail off over time, which means where you are when hired really does matter more the more experienced you get. Based on informal observation, most (not all) good engineers tend to improve slightly sub-linearly, so it's even more tilted.