• by Joe Mandese  @mp_joemandese, January 14, 2011

Nielsen Thursday said it is delaying a plan to add duplicate viewing of TV shows to its national TV "currency" ratings two months until April 1. Nielsen said it would move forward with its original plan to add the duplicate viewing data to its "respondent-level data," which are the building blocks of its national TV ratings, as originally planned beginning Jan. 31, but said it needed additional time to make the adjustments necessary to the "currency" systems and reports that advertisers and agencies use to buy national TV time from networks.

Nielsen did not explain why it needed more time, but said the changes are critical to its plans for developing its so-called "extended screen" ratings, which will also incorporate viewing of TV shows that watched online. Those extended screen ratings are still slated to launch in late April, according to Nielsen's update.

"The change in this calculation and the change in the [households using television] calculation are being made to provide improved insight into how and when people are spending time with television programming in a television environment that includes multiple platforms and means of time-shifting viewing schedules," Nielsen stated in Thursday's announcement.