From U.S. News and World Report :
The reason, explains PayScale.com lead economist Katie Bardaro, is that for many jobs
, experience eventually stops improving one's productivity. "You reach a point in middle-age where there is no more learning you can do in your job
," says Bardaro. As a result, you stop receiving pay increases for increased competency. (PayScale.com's figures take inflation into account; workers do receive small pay increases as they approach retirement, but they largely reflect inflation and not a real wage hike.)
There are some exceptions to this general rule: Some professions, in which experience continues to add value, continue to see salary growth. Tech-heavy jobs are one example, along with lawyers and engineers, says Bardaro. "You're constantly learning [if you're a lawyer]: How to get clients to trust you, the law, how to win cases," she adds.
In other professions, such as non-physician healthcare positions, the learning curve drops off more abruptly. For pharmacists and nurses, Bardaro says, "You learn everything you need to know to do your job in school or in the first few years of doing it, so you don't have much more to learn." Those positions tend to start off with relatively high pay but don't grow as workers get older.
The gender difference in the age at which salaries flatten is largely explained by job choice, says Bardaro. Men tend to gravitate toward jobs in which growth continues (such as engineering) while women often work in fields with flatter pay curves (such as teaching, nursing, and social work).