The average age of Facebook users has started to decrease yet teens continue to leave the platform—a trend it won’t be able to reverse this year, according to eMarketer.

Between 2020 and 2025, the firm estimates Facebook will lose 1.5 million teen users. Among internet users between 12 and 17 years old, only 35.3 percent will use the platform this year. Less than a third of this group are anticipated to use it in 2024.

By 2023, there will be 34.7 million Gen Z and just 33.1 million baby boomers who use Facebook in the US—a gap that is and will continue to widen through 2025. Aging, eMarketer notes, is the key driver here: as Gen Z grows up, some will join (or rejoin) Facebook while baby boomers are also growing older and aging out of social media.

Regardless of how Gen Z and baby boomers interact with the platform, its main users are millennials and Gen X users, who together now account for more than half of the platform’s user base.

Facebook will have gained roughly 9 million users in the US between 2020 and 2025—more than enough to counter the platform’s loss of teen users and maintain its penetration rate among internet users into 2025.