Here's something I learned: Nielsen is known for collecting data for both TV and radio, but I had no idea that they ranked TV on twitter. I figured there had to be something, but hey you learn something new everyday.
Here's how they consider and collect the data.
Nielsen Twitter TV Ratings Daily Top Five lists are ranked by Tweets and include two metrics for each of the top Series and Specials episodes or Sports Events.
Tweets – Tweets ascribed to a linear TV episode.