When “Grey’s Anatomy” had its season premier in late September, Nielsen believes that 9.3 million watched the episode. However, only roughly 99,000 people mentioned the show on Twitter. Conversely, NBC’s “The Voice” only had an audience of 3.8 million, but tweets on the episode were seen, in theory, by 2.7 million Twitter accounts after 225,000 people tweeted potential spoilers.

Nielsen grey anatomy

Nielsen measuring TV shows ratings

As a result, Nielsen has determined that it’s high time that they began measuring what the ratings company is calling the “unique audience.” Beginning tonight, Nielsen will begin compiling what its calling the ‘Nielsen Twitter TV Ratings’ after announcing that it would begin measuring the phenomenon that is social TV. While it’s yet to impress television executives, Nielsen will go ahead with or without them.

“We feel this is going to be a credibility-building moment for the industry,” said Andrew Somosi, the chief executive of SocialGuide, an analytics company that Nielsen acquired last November, in part to create the new product.

Television platform important for Twitter

Twitter believes that television is an important part of its platform. In the prospectus for its IPO, Twitter used the word television 42 times, and believes that its user base spurs viewership of television programs. And that is just the tip of the iceberg. “The full iceberg is the extent to which people are seeing those tweets.” Even though only 225,000 people tweeted about Grey’s Anatomy, those tweets reached over ten times that, with 2.8 million distinct Twitter accounts receiving the tweets.

Nielsen’s numbers have always been used by networks to promote their shows. Nielsen clearly believes that by providing this coverage, Twitter mentions that it expects networks will begin marketing their shows based on this additional metric. Nielsen has so far kept mum about how many customers will be paying for its Twitter TV ratings, and the news release about the new product only mentioned two companies by name—Discovery Communications and ad-buying giant Universal McCann.

“This is just the beginning; the data hasn’t been available until now,” said Sean Casey, who founded SocialGuide and is now its senior vice president for product.

Not everyone is sold on the strength nor breadth of Nielsen’s Twitter ratings.

Ed Keller on TV shows conversations

“What people often lose sight of is the fact that the overwhelming majority of conversations about TV shows still take place offline,” said Ed Keller, the chief executive of the Keller Fay Group, a market research firm that specializes in word of mouth information. Suffice it to say the data that Keller Fay Group provides to networks like CBS will lose value if Twitter ratings truly take off as Nielsen expects.

The firm’s surveys consistently indicate that 80 percent of conversations about TV shows happen in person and 10 percent happen on the phone, with most of the remaining 10 percent occurring online.

“The conversations that take place in the real world can often be quite different from those that take place on social media,” Mr. Keller said.