The decline is sharper among younger users, according to Edison Research.
Facebook has an estimated 15 million fewer US users today than it did in 2017, according to Edison Research data published Wednesday.
In 2017, 67 percent of the total US population over the age of 12 used Facebook, the data says. In 2018, that number dropped to 62 percent, and then it dropped again, to 61 percent, in 2019. That comes out to an estimated 172 million current users, according to Edison Research.
The drop-off has been higher among younger users. In 2017, 79 percent of Americans between the ages of 12 and 34 used Facebook, the data says. That number decreased to 67 percent in 2018 and 62 percent in 2019. That equates to around 82 million 12- to 34-year-old Facebook users in 2017, compared with 65 million users today.
Younger Americans' use of Facebook-owned Instagram, on the other hand, has grown from 64 percent in 2017 to 66 percent in 2019, according to Edison Research. The percentage of Snapchat users in this demographic remained at 62 percent in the past two years. Twitter saw a drop in 12- to 34-year-old users, from 36 percent in 2017 to 29 percent in 2019.
Meanwhile, among users aged 55 and up, Facebook use increased from 49 percent in 2017 and 2018 to 53 percent in 2019.
Despite the overall decrease in use, Facebook remains the most popular social media platform for Americans age 12 and up. In 2015, 65 percent of social media users said Facebook was the brand they used most often. That number dropped to 52 percent this year, still beating out platforms like Instagram (16 percent) and Snapchat (13 percent) by a landslide.
Facebook is also still the most-used platform for 12- to 34-year-olds in the US, though the percentage of people in that demographic who said it was the brand they used most decreased from 58 percent in 2015 to 29 percent in 2019.
Edison Research conducted the study by interviewing 1,500 random people aged 12 and up in January and February via phone. The company's findings don't appear to line up with the number of monthly active users Facebook reported in its most recent earnings report, which it said had increased from 2016 to 2018 in the US and Canada.
Facebook declined to comment.