According to new estimates by eMarketer, Facebook users in the 12- to 17-year-old demographic declined by 9.9 percent in 2017, or about 1.4 million total users. That's almost three times more than the digital measurement firm expected. There were roughly 12.1 million U.S. Facebook users in the 12- to 17-year-old demographic by the end of the year. Recode reports: There are likely multiple reasons for the decline. Facebook has been losing its "cool" factor for years, and young people have more options than ever for staying in touch with friends and family. Facebook also serves as a digital record keeper -- but many young people don't seem to care about saving their life online, at least not publicly. That explains why Snapchat and Instagram, which offer features for sharing photos and videos that disappear, are growing in popularity among this demographic. Overall, eMarketer found Facebook lost about 2.8 million U.S. users under 25 last year. The research firm released Facebook usage estimates for 2018 on Monday, and expects that Facebook will lose about 2.1 million users in the U.S. under the age of 25 this year.