A new report from eMarketer forecasts that Facebook and Instagram will control nearly 65 percent—the equivalent of roughly $16.3 billion—of brands' social-media budgets this year, while Twitter's share will fall.
The research firm said today it expects overall social ad spending to hit $25.1 billion in 2015, up from a $23.7 billion projection in April. EMarketer's estimates are largely driven by Facebook and Instagram's ad business, which is expected to grow 42 percent from 2014.
After opening its promos to all advertisers a few months ago, Instagram will bring in $600 million this year, or about 5 percent of Facebook's total ad revenue, according to eMarketer. By 2016, the app will generate about $1.5 billion in ad revenue, a 149 percent year-over-year jump.
Globally, Facebook will make nearly $12.80 in ad revenue off of each user this year and $48.76 in ad revenue off of individual U.S. users, eMarketer said.
While advertisers are starting to buy more Instagram ads, the app's user base is also growing quickly. Yesterday, the photo-sharing platform announced it has 400 million monthly users, up from 300 million earlier this year.
Meanwhile, Twitter is expected to lose a bit of steam, according to the report. The microblogging site is expected to pull in a little more than $2 billion in ad revenue (or roughly 8 percent of total spend), growing nearly 62 percent over 2014's revenue. In April's forecast, eMarketer expected Twitter's ad revenue to grow 67 percent this year.
EMarketer cited Twitter's slowing user growth as part of the reason for the drop in projected ad revenue. Internationally, Twitter will make $7.75 per user this year and $24.48 each off of its U.S. users.
"Twitter has improved its ad targeting capabilities, and it still has a lock on real-time conversation," principal analyst Debra Aho Williamson said in a statement. "However, advertisers want to reach a mass audience, and that's harder to do on Twitter than on Facebook."