This year, for the first time, more than half of the US population will use Facebook, according to eMarketer’s latest social network usage forecast. In 2016, 50.3% of Americans of all ages will be on Facebook at least once a month, up from 49.3% in 2015.

Facebook will remain the dominant social network by a wide margin through at least 2020, the end of eMarketer’s forecast period.
This year, 162.9 million US internet users will log on to the site at least once a month. Facebook-owned Instagram, the second-most-used social network, will have 89.4 million US users this year, or 27.6% of the population. Twitter is a distant third, with 56.8 million users this year, representing 17.5% of the US population.

“Facebook remains the king of social networks, and the usage increases are coming primarily from people who are Generation X and older,” said eMarketer principal analyst Debra Aho Williamson. “Plenty of teens and young adults still use Facebook, but growth is slowing in these groups.”
As a result of Facebook’s strong usage rates, it will continue to command the lion’s share of US social network ad spending. This year, Facebook will capture 73.4% of social network ad spending in the country, or $9.86 billion. Twitter is a distant second, on course to capture 13.8% of US social network ad dollars, or $1.86 billion.
Another important milestone for Facebook this year is that more than half of US mobile phone users will be Facebook users. In 2016, 52.9% of mobile phone users will log on to Facebook at least once a month from their mobile phone. And mobile will continue to play an important role in Facebook”s growth. This year, 86.0% of US Facebook users will access the platform through a phone, with that figure climbing to 91.0% by 2019. Strong user engagement on mobile is helping to drive Facebook’s mobile ad revenues, which this year will amount to 19.2% of total mobile ad spending in the US (Google is No. 1 with a 31.7% share).

Even with Facebook’s explosive growth in mobile, Twitter still leads in terms of the percentage of users who access the service via mobile, as well as in the percentage of revenue from mobile. This year, 92.3% of Twitter’s users will log on via their phones. And while Facebook is expected to derive 82.0% of its US ad revenues from mobile this year, eMarketer forecasts that 90.0% of Twitter’s ad revenues this year will come from mobile.
“Twitter and Facebook are far ahead of other companies in the percentage of ad revenue that comes from mobile. They are helping to convince marketers that mobile is important to their business strategy,” said Williamson.