Mark Zuckerberg, CEO and founder of Facebook Inc., attends a conference in Idaho in July 2017. Zuckerberg has announced — and celebrated — a drop in the amount of time users are spending on Facebook.

Mark Zuckerberg, CEO and founder of Facebook Inc., attends a conference in Idaho in July 2017. Zuckerberg has announced — and celebrated — a drop in the amount of time users are spending on Faceboo