According to a Pew Internet & American Life Project survey, social networking amongst internet users aged 50 or older has risen from 22% to 42% during the past year.
47% of internet users aged between 50 and 64 now use social networking sites, compared to 7% in 2005.
In April 2009, the figure was 25%, and by December 2009 it was 36%.
The survey also found that 26% of internet users aged 65 or older now use social networking sites, compared to 5% in 2005.
This figure was 13% in April 2009, and by December 2009 it was 22%.
Social networking also increased amongst other age groups, with 61% of internet users aged 30 to 49 now using sites such as Facebook or Twitter, compared to 12% in 2005.
This is a small increase from December 2009, when 58% said they used social networking sites.
The age group with the highest number of internet users who use social networking sites was the 18 to 29 group, with a figure of 85% as of May 2010.
This is a significant increase from 16% in September 2005.