Reputation.Com, headed by CEO Michael Fertik, examined common doctoral degrees and found that persons who hold them have seen their careers accelerate by more than 10% on average in terms of compensation (sadly, with the exception of the humanities and education). This research is discussed in a recent Linked In article by Fertik himself.
According to Fertik, the hard sciences, such as chemistry and physics, along with doctoral degrees in fields such as marketing and economics, all make the cut. These degrees typically lead to higher wages and a greater increase in wages over time.
Granted – nothing is life is for certain, but as of now, the Ph.D. seems like it has made a comeback.