From Pew Research:
...a national survey of 1,520 adults conducted March 7-April 4, 2016, finds that Facebook continues to be America’s most popular social networking platform by a substantial margin: Nearly eight-in-ten online Americans 1 (79%) now use Facebook, more than double the share that uses Twitter (24%), Pinterest (31%), Instagram (32%) or LinkedIn (29%). On a total population basis (accounting for Americans who do not use the internet at all), that means that 68% of all U.S. adults are Facebook users, while 28% use Instagram, 26% use Pinterest, 25% use LinkedIn and 21% use Twitter.
Thanks in part to the growing number of older adults who are joining the site, Facebook use appears to be on the rise: The share of online adults who report using Facebook has increased by 7 percentage points compared with a Pew Research Center survey conducted at a similar point in 2015. In addition, the share of Facebook users who check in daily has increased slightly in the past year: 76% of Americans who use Facebook now report that they visit the site on a daily basis, up from 70% in 2015.
79% of internet users (68% of all U.S. adults) use Facebook
32% of internet users (28% of all U.S. adults) use Instagram
24% of internet users (21% of all U.S. adults) use Twitter
29% of internet users (25% of all U.S. adults) use LinkedIn
31% of internet users (26% of all U.S. adults) use Pinterest
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