Nielsen will launch its Twitter TV Ratings on September 30, giving television networks and advertisers the first industry-standard metric for second-screen viewership.

Twitter has confirmed that date to Marketing Land, after it was first reported by the Wall Street Journal. The WSJ article also includes some of the ratings service’s initial test results:

Early findings showed that for every one tweet about a TV show, roughly 50 people see it, the company says.

Original reports said that the plan was to have the Twitter TV Ratings service ready by the time the fall TV season began. That’s already underway, making the September 30 launch date about two weeks late. But Twitter, TV networks and the advertisers will surely still welcome the new data with open arms.

Nielsen isn’t only focusing on Twitter. The WSJ says Nielsen will supplement its traditional TV ratings with data related to TV viewing on tablets and smartphones, but that won’t begin until the 2014 fall TV season.

The Twitter-Nielsen partnership was announced late last year and helped solidify Twitter as the primary driver of social TV viewing. Facebook has gone out of its way this year to let the world know that its users help drive TV ratings, too, but advertisers seem most interested in Twitter at this point. And that’s something that bodes well as Twitter approaches its IPO, which is likely to happen later this year.