Earlier quoted context omitted.
Oh, that's an interesting question. I've seen a graph of (US) advertising spend vs GDP which seems to hold constant over the last 70 years. But to lump all FB/snap/twitter into entertainment+advertising and get % of the population working for those companies would be interesting.
But then you start doing violence to the categories. Twitter/Facebook certainly have entertainment functions, but they also have tentacles reaching deep into publishing and news. Now, suddenly a like for like comparison needs to include newspapermen, typesetters, printers and papermill workers.
But seriously, I hope data-minded grad students/sociologists are investigating this more.