By "UX designer", I mean those who are practicing one or more of the following as their profession: Information architecture, interaction design, visual design, or user research. I'm just trying to get a sense of how large our profession is without precipitating another heated debate about the "UX designer" moniker.
Yes you are right. It is a little subjective because it depends on what term you use and where you go. Every country is different.
According to LinkedIn stats, dated as of today there are over 900,000 UX Designers on the LinkedIn network.
You can read more and about the evolution of UX as a career here: http://speckyboy.com/2012/12/13/the-dark-side-of-user-experience-design/