The Pew Internet & American Life Project reports that 19 percent of Internet users now say they use Twitter or another service to share updates about themselves or to see updates about others. That’s a significant increase over a year earlier, when only 11 percent said the same. Three groups are mainly responsible for driving the growth: social network website users, those who connect to the Internet via mobile devices and Internet users under age 44.

Source: PewInternet.org, 2009