11 percent of online US adults use Twitter or similar status updates, according to the Pew Internet and American Life Project. (pdf) The 11 percent in December 2008 nearly double’s the total of a half year before, as only 6 percent had sent a Twitter-like communiqué in May of Last year. In fact, the percentage of people sending status updates grew 2 percent between November and December alone. As expected, status updates are most used by younger users. 19 percent of those in the 18-24 group have used Twitter or a similar service, and 20 percent of those in the 25 to 34 group have. This is a much different world than the one last year, in which Zappo’s Tony Hsieh was told by a group of students at Indiana University (my alma mater – Go Big Red!), that Twitter “was only for old people.”

Old people, in fact, are much less likely to use Twitter than those young Hoosiers reported. Only half of 35 to 44-year-olds, 10 percent, are as likely to tweet as the group immediately younger than them.

And again that percentage is halved as age increases: 5 percent of those between 45 and 54 send status updates, 4 percent of those between 55-64 tweet, and only 2 percent of those 65 and older share their day’s minutiae via social networks (that's why they have grandchildren).

Pew does note, though, the average Twitter user is older than users of other social networks. The median Twitter age is 31, while MySpace is 27, and Facebook, 26.

Interestingly, people in lower income categories are more likely to tweet than those in the higher. Pew attributes this to the dramatic age difference, which makes sense.

Wireless users are more than twice as likely than non-wireless users to send status updates (14 percent to 6), indicating that tweeters are most likely to be mobile users, whether on laptops or hand-held devices. Pew notes that Twitter users are more likely to access other Web services with their phones.

23 percent of people who used other social networking tools also use Twitter, while only 4 percent of people who do not use other social networks tweet. 27 percent of bloggers tweet, as compared to the 10 percent of non-bloggers who do.

Twitter users are also more urban: 35 percent live in urban areas, a much bigger spread than the 9 percent of rural tweeters (not including, of course, the birds. Ha!)

By Mark Alvarez