I've been bearish on the proportion of marketing dollars and time focused on Facebook.
Of course, every specific demographic is different - B2B vs. consumer products, teens vs. parents. Still with the same pot of resources, I would not put more toward Facebook, but divert some of those to other areas.
Nielsen just released yoy figures:
"'Overall, including Facebook, Messenger, Instagram and WhatsApp, Facebook's share of digital consumption was at 15.2% vs. 16.9% in the year-ago period,' according to recent research by Pivotal's Brian Wieser."
"The Nielsen data wasn't the only bad news for Facebook. A new study of teens by Common Sense Media cited by the news website Axios found that only 15% of those ages 13 to 17 said their "go-to social site" was Facebook, down from 68% in 2012."