According to research compiled by Hubspot, Facebook ad revenue grew from just under $2 billion in 2010 to $12.5 billion, with ads on the popular social platform accounting for “more than 9% of total digital ad spending and 18.4% of global mobile digital advertising.”
https://www.forbes.com/sites/sujanpatel/2017/02/04/10-mistakes-newbies-make-with-paid-facebook-ads/#14d325812d2a/