The percentage of adult Internet users on Twitter "has more than doubled since November 2010," Pew reports.

People 18-29 are the heaviest users of the platform, but numbers are growing for other age groups. In fact, the percentage of seniors who use social networking sites has tripled since 2009, Pew reports: 43 percent of people over 65 use them now.

Previously: 16 percent of online Americans use Twitter