Pew Internet has a new report out on American adults’ use of social media for various political purposes. In their nationally representative sample:

• 85% of the respondents are internet users
• 69% of the internet users say they use social networking sites
• 16% use Twitter

This translates to 60% of all American adults using either a social networking site (like Facebook, LinkedIn, or Google+) or Twitter.

Interesting infographic showing activities by demographic:

Full report is here: http://www.pewinternet.org/Reports/2012/Political-engagement/Summary-of-Findings/Overview.aspx