As of May 2013, 72% of US adult web users use social networks. That's up from 67% in just 5 months. Twitter has driven some of the growth, with user numbers rising to 18% in May, up from 8% in November 2010.. While social networks including Twitter are most popular with young adults, the micro-blogger's audience has grown across all age groups.
There are differences in demographic breakdown on Twitter vs. social networks overall. General social use skewed female, an eMarketer anaylisis of the Pew study found: 74% women vs. 70% men. But On Twitter, the breakdown was more gender neutral.