NOW IT'S LETTER OF RECOMMENDATION SEASON. Dani Rodrik speaks the truth.

As I always tell students asking me for advice on this, the only good reason to want to do a Ph.D. is that you want to be an assistant professor at some academic institution. If you want to deepen your knowledge or enhance your credentials, go and work out there for four or five years (past a high-quality master's program), and you will be infinitely more ready to rise up in the world than if you had spent that time doing a Ph.D. And having done well in a master's program, or having enjoyed it, is no guarantee that you are suited to a Ph.D. program.

See also this.