In February 2013 Pew Research released their research on the Demographics of Social Media. Which has some interesting data such as:
77% of the average age of social media users are between 30-49
71% of women use social media versus 62% of men
The household income of top social media use is less than $30kThe ethnicity breakdown is:
Hispanics 72%
Black, Non-Hispanic 68%
White, Non-Hispanic, 65%
I was also interviewed by USA Today about the diversity of social media use in an article called: Minorities rush to Twitter, Instagram, smartphones
H/T: Divas & Dorks