https://www.techdirt.com/articles/20181220/09395141272/cbs-eyes-ditching-nielsen-as-streaming-cord-cutting-change-game.shtml

For years, we've noted how popular TV ratings firm Nielsen has turned a bit of a blind eye to cord cutting and the Internet video revolution, on one hand declaring that the idea of cord cutting was "pure fiction," while on the other hand admitting it wasn't actually bothering to track TV viewing on mobile devices. It's not surprising; Nielsen's bread and butter is paid for by traditional cable executives, and really, who wants to take the time to pull all those collective heads of out of the sand to inform them that their precious pay TV cash cow is dying?

Eventually, the cord cutting trend became too big to ignore, forcing Nielsen to change its tune and start acknowledging the very real trend (though they called it "zero TV households" instead of cordcutters). Broadcasters (especially those hardest hit by cord cutting) didn't much like that, and began bullying the stat firm when it showed data that didn't jive with the view a foot below ground. While Nielsen slowly improved its methodologies, it would occassionally back off on certain data collection and reporting changes if the cable and broadcast industry complained loudly enough.