To WWW or Not to WWW - that is the question

I am curious as if any one has / knows of true data on what is more common - to use www or not to use www.

Google Webmaster tools prefers one or the other, and they do not make a preference. I thought that dropping www was becoming more popular and that most people do not use it anymore.

Talking with a client today, she said most people still use www. I would like to back up my statement that it is NOT used as much by having some documented research (or learn that people are still using it).

Am I looking for something that does not exist?

Thanks in advance!