Nearly three-quarters (72%) of online US adults were using social networking sites as of May 2013, up from 67% in late 2012, according to a recent report from the Pew Research Center's Internet and American Life Project.

When Pew first started asking about social networking sites in February 2005, just 8% of online adults said they used social networks.

Social networking site use is prevalent for Internet users from a wide range of demographic groups. Not surprisingly, younger adults are heavily represented, but social networking continues to grow in popularity for older adults as well.

Below, additional key findings from the Pew report, which was authored by Joanna Brenner and Aaron Smith.

Not Just for Kids 

• Six out of ten Internet users age 50-64 are social networking site users.
• Adoption rates for those 65 and older have tripled in the last four years (from 13% in the spring of 2009 to 43% in 2013).