The revelations came during a briefing with cable network clients on Nielsen's plans to begin "weighting" - or mathematically adjusting - its ratings to make sure they accurately represent all U.S. households, including those with computers connected to the Internet.
The briefing was part of an annual review Nielsen conducts each year around this time to ensure that its national TV ratings sample corresponds with key characteristics of the U.S. population. In preparation for the 2010-11 TV season, Nielsen said it looked at weighting for three household characteristics: The presence of computers connected to the Internet; the presence of high-definition TV sets; and splitting its "under 35-year-old" head of household demographic break into those under the age of 25 and 25- to 34-year-olds.
Nielsen said it scrapped the idea of weighting for presence of high-definition TV sets, but recommended the other two weighting controls, and set a deadline of Monday to make a decision, citing "technical" reasons.
But the rush to begin controlling the weight of households with computers connected to the Internet has caused a stir among some clients, because they normally receive full-year of comparison data before making such a change, but have only gotten one-week of data analyzing the impact of weighting TV ratings based on the computers connected to the Internet.
Nielsen said the reason for the crunch is that it only recently compiled estimates for how many households in the total U.S. population have computers connected to the Internet (69.7%), and that it needs to make the adjustments in time for the start of the 2010-11 TV season in September.
Based on its analysis, Nielsen estimates that its national TV ratings sample currently over-represents households with computers connected to the Internet by about 1.7%, which means it would mathematically reduce their representation in the ratings.
Nielsen executives say the actual impact on ratings would be negligible, except for a brief period around the Christmas holidays when U.S. households tend to add new consumer electronics, including computers and broadband Internet access. But some clients believe the change will negatively impact ratings for networks that skew young, and boost the representation of networks that skew old.
Meanwhile, Nielsen executives confirmed that they currently have no plan to measure the impact of TV viewing done via Apple computers connected to the Internet, and also said they would not necessarily measure viewing done via all other computers connected to the Internet in its ratings sample.