Nielsen, and Twitter today announced an agreement to create the "Nielsen Twitter TV Rating" for the US market, a metric that is based entirely on Twitter data.

Under this agreement, Nielsen and Twitter will deliver a syndicated-standard metric around the reach of the TV conversation on Twitter, slated for commercial availability at the start of the fall 2013 TV season.

TV viewers discuss TV on Twitter, creating a new dynamic between audiences and programming. The service's more than 140 million active users send one billion Tweets every two and a half days, the vast majority of which is public and conversational, making Twitter data a necessity in producing standardized metrics representing online and mobile conversations about television.

"As the experience of TV viewing continues to evolve, our TV partners have consistently asked for one common benchmark from which to measure the engagement of their programming," Chloe Sladden, Twitter's vice president of media, said in a post on the company blog on Monday. "This new metric is intended to answer that request, and to act as a complement and companion to the Nielsen TV rating."

The Nielsen Twitter TV Rating will serve to complement Nielsen's existing TV ratings, giving TV networks and advertisers the real-time metrics required to understand TV audience social activity.