The number of adults using social media sites increased to 65% according to a new survey from the Pew Research Center’s Internet & American Life Project.

It’s the first time more than 50% of all adults said they’re sites like Facebook, LinkedIn or MySpace, and a dramatic increase from the first survey in 2005, which showed that just 8% of internet users or 5% of all adults said they used them.  While 61% of users over the age of 30 reported they use social networking site on a typical day, it remained relatively flat over the last year.

Usage by those 65 and older grew more than any other group, with 33% of the cohort saying they use the sites, up from 26% last year.

“The graying of social networking sites continues, but the oldest users are still far less likely to be making regular use of these tools,” said Mary Madden, Senior Research Specialist and co-author of the report. “While seniors are testing the waters, many Baby Boomers are beginning to make a trip to the social media pool part of their daily routine.”

In the past two years, social networking site use among internet users age 65 and older has grown 150%, from 13% in April 2009 to 33% in May 2011. Similarly, during this same time period use by 50-64 year-old internet users doubled—from 25% to 51%.

View the report.