The research firm found that the Facebook-owned photo- and video-sharing network’s U.S. user growth rate slipped to 6.7% in 2019 from 10.1% in 2018, and eMarketer projected a continued decline.

eMarketer—which uses its own methodology to arrive at its forecasts and estimates—revised its U.S. growth rate projections for Instagram for the next two years downward, to 4.5% in 2020 from 5.4%, and to 3.2% in 2021 from 4.1%.

The company said older age groups are not joining the platform as quickly as it originally anticipated, and the resurgence of Snapchat and rise of TikTok will make it difficult for Instagram to sustain any kind of high growth.

However, eMarketer believes Instagram’s ad revenue in the U.S. will continue to grow at double-digit rates, driven by the introduction of ads in the application’s Explore tab, as well as the growth of shoppable ads.

The company said Instagram generated $9.45 billion in U.S. ad revenues in 2019, and it sees that figure jumping 46.6% in 2020, reaching $13.86 billion.

eMarketer junior forecasting analyst Nazmul Islam said in an email, “Instagram is doing really well—it is the second-most internet-penetrated social media platform in the U.S. behind Facebook and, despite increased pressure from competition, we expect it to maintain its second-place position with a good gap from the rest of the platforms.”