The rec.arts.tv FAQL:

Last updated:  February 1, 2004.
This version:  8.00
Note: The date of the last update is the date of the last change to this section; lack of an update since then means that the contents of this particular section are still true or valid to the present day. This page will be updated with every new major update (i.e. version x.00) of this FAQL, however.

Section 1.1.3: "How do ratings/Nielsens work?"

Answer: This may be the most complex question asked by people in rec.arts.tv, and perhaps only the A.C. Nielsen Company (specifically, NielsenMedia) knows all the answers for sure.

Why ratings are collected is much simpler question. The broadcast and cable networks, as well as local TV stations, need to know the actual number of viewers that are tuning in, as well as the percentage of total viewers tuned into the particular station/network in question (this is known in Nielsen terms as the ratings "share"), and also the type of viewer tuning in (e.g. the demographics). All this information is then used by the network and/or station to set the advertising rates for sponsors (see Section 3.6: "What is 'sweeps'?" for more information).

How ratings are collected is fairly straightforward, as well. There are two methods of collecting ratings information:

  1. Overnight Ratings: These ratings are collected in many of the largest (i.e. urban) TV markets) for immediate (overnight) analysis.
  2. National Ratings: These ratings are collected over the course of a week by people who record what they watch in Nielsen "log books".

It's how sample members are chosen, and how the ratings information is analyzed that's much more of a mystery. According to the A.C. Nielsen Company, the National Ratings are a cross-section of 4,000 (American) TV households; how this sample is chosen is not well known. To avoid the possibity of influencing of participants by either broadcasters or advertisers, the identities of Nielsen participants are kept secret.

For National Ratings, the TV viewers in the household are told to log what they watch for Nielsen. The logging of TV viewing is done by members of the household in the infamous Nielsen "diary" (or by electronic means). Each diary contains entries for one week (a new diary is sent to participants weekly). The viewing circumstances of each member of the household (including guests) is then supposd to be logged in the diary (in 15 minute increments) everytime anyone in the household watches TV. The dairy also contains entries in the back for the recording (and later viewing) of TV shows by simulataneously recorded VCR tape. For demographic purposes, the age, sex, ethnicity, etc. of the viewer(s) is also recoreded in the Diary.

All this data is then sent to the Nielsen company on a weekly basis (or in the case of the Overnight Ratings, on a daily basis), where it is compiled by Nielsen. In this way, the "Nielsen families", as these households are called, are used to represent the larger (American) TV viewing audience in much the same way that polls of roughly 1,000 people are used to represent the views and opinions of the (American) public.

The key questions here are, 1) How does the Nielsen company select the households it uses to determine TV ratings?, 2) How accurate are the viewing logs kept by these "Nielsen families", and how is this data compiled?, and 3) Overall, how accurate are the Nielsen ratings? Only the Nielsen company knows the answer to the first two questions. As for the last question, there are a number of people who are skeptical as to the accuracy of the Nielsen ratings. Nontheless, ratings from the Nielsen company are widely used and followed.


Go to:
[Section 1.1]
[FAQL] [FAQ Intro]
[TV Page]

ijball@mac.com