Looking ahead to key digital trends in 2019, eMarketer's analysts render a bad news/good news pair of predictions for Facebook.

While the social network will face serious problems with user engagement, Facebook, in tandem with Google, will continue to dominate digital ad revenues.

In the US, growth in Facebook user time has come to a halt. We predict daily time spent with Facebook will average 40 minutes in 2019, right where the figure was in 2016.

And since overall time spent with digital is still growing (albeit modestly), Facebook now accounts for a declining proportion of this total. In 2016, Facebook accounted for more than half (53.0%) of time spent with social. But the figure has been on a downward trajectory, heading toward 44.6% in 2019, according to our forecast.

In our report—Ten Key Digital Trends for 2019: Our Predictions for What Will Matter to Marketers, and What Won't—we note that Facebook cannot rely on Stories to shore up user engagement. “It hasn’t cracked the code on getting more of its users to use Stories, despite its popularity on Instagram,” according to the report. Nor can Facebook count on video content (via its Watch video-on-demand service) to keep users involved, as its efforts in that area have had mixed success. The upshot is that user engagement with Facebook will be highly dependent on its feed, the venue where it has struggled to cope with fake news and negative content, among other problems.

All that said, we also predict that Facebook will hold up its end of the Facebook-plus-Google duopoly’s dominance of digital ad revenues for at least another year. We expect the company’s worldwide ad revenues will grow from $39.94 billion in 2017 to $55.44 billion in 2018, on the way to $67.25 billion in 2019.

We do anticipate a decline in the duopoly’s share of total US digital ad revenues, but hardly a precipitous plunge. Looking at US digital ad spending for 2018, the duopoly was expected to have garnered 57.7% of the total. By 2020, this figure will dip to a not-so-mere 55.9%, with a gain by Amazon taking up the slack.

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