Facebook dominates social media usage
The data is from circa 2012-2014:
For the first time in Pew Research findings, more than half (56%) of internet users ages 65 and older use Facebook. Overall, 71% of internet users are on Facebook, a proportion that represents no change from August 2013.
Source: Social Media Site Usage 2014 | Pew Research Center
70% of Facebook users log in to Facebook daily.