Television Audience Measurement – Methodology
Who are Nielsen TAM?

Nielsen Television Audience Measurement have been providing the ratings measurement service in Ireland since 1996. Their current measurement contract runs from 1st September 2017 until 31st August 2019.

Nielsen measure over 40% of the world’s TV viewing behaviour in multiple countries across 5 continents.

How do they measure TV audiences?

Nielsen TAM gather information about Irish television viewing from a nationally representative panel of 1,050 homes. This equates to approximately 2,500 panel members every day. They measure viewing on every set within each panel home. Since September 2010, Nielsen TAM have also been measuring time-shifted viewing (TSV). Time-shifted viewing that takes place within 7 days of the original broadcast is included in audience ratings.

The Establishment Survey

A large household survey called the Establishment Survey is conducted 2 times a year to establish the size and nature of the television population in Ireland. The fieldwork for the survey is carried out by Behaviour & Attitudes, Ireland’s largest independent market research company, on behalf of Nielsen TAM. The survey is one of the largest face-to-face random probability surveys carried out in Ireland. The sample size exceeds 2450  interviews per wave (7350 per annum)  with fieldwork conducted on a continuous basis throughout the year.

The Establishment Survey is a household-based survey. The questions are asked of the main grocery shopper in each household, i.e. the Housekeeper, but they are encouraged to get help answering from other members of the household.

Data from the Central Statistics Office is used to weight the results of the Establishment Survey to ensure that the panel is representative of the television household population in terms of age, region and sex. AIMRO data is used to weight the responses by social class.

Information derived from the Establishment Survey includes:

  • TV Universes
  • Reception Type
  • Channels Received
  • DVD Penetration Levels
  • PVR Penetration Levels
  • Number of TV Sets per Household
  • Games Console Penetration Levels

Many other details that relate to, or may affect TV viewership, are also collected.

Panel controls and universes are derived from the weighted data. These are updated 3 times a year to ensure that the service keeps pace with consumer and population developments.

The Panel

The panel is designed to be representative of the television population as defined by the Establishment Survey. Households meeting the demographic requirements are invited to join the Nielsen viewing panel. In September 2009, there were 670 homes on the panel. Under the terms of the new contract, this rose to 800 homes in September 2010, 920 in 2011 and 1,050 in 2012. There are currently 1,050 homes on the panel, which is one of the largest per-capita panels in Europe and one of the most representative.

The Peoplemeter

A device called a Peoplemeter is installed on every TV set in all panel homes. It monitors the viewing of everyone in the household (and guest viewing). The peoplemeter is a small box that looks like a decoder which sits on top of the TV set. Every member of the household is assigned a button on a special remote control which they use to log in and out of their viewing.

Viewing to all sets in the homes (including time-shifted viewing via Personal Video Recorders) is measured by the Nielsen UNITAM meter. This is state-of-the-art technology, capable of working with all modern TV sets and associated equipment. The UNITAM meter is new to Ireland but has been tried and tested in many markets in recent years. It represented a very substantial investment in new equipment but will “future-proof the measurement service for many years.”

The Reference Site

The Peoplemeter is connected to the telephone line in the household. In the early hours of the morning (between 3 – 6am), the central computer in Nielsen TAM’s office dials each of the panel member households and collects the viewing data. Minute-by-minute ratings data collected by the UNITAM meter is downloaded every night from each panel home for every member of the household aged 4+. The data then goes through a rigorous quality control system. Central to this is the reference site which cross-checks reported viewing on the meter with actual transmissions by over 200 channels. As part of the new measurement contract with Nielsen TAM, the reference site has been totally upgraded at a significant capital cost.


As mentioned in the section above, Nielsen TAM collect viewing data down to a minute-by-minute level. This results in the delivery of a huge amount of data on a daily basis. Making the viewing data accessible to all users requires powerful software.The current measurement contract included significant upgrades to the Arianna software, which is used by all broadcasters and advertising agencies to analyse TV viewing trands and monitor advertising campaigns.

Time-Shifted Viewing (TSV)

Modern technology allows the consumer to watch what they want when they want using PVRs. In the most recent Establishment Survey (September 2012), 45% of Irish TV homes claimed to have a PVR. The new measurement contract requires that such viewing be capable of measurement.

The UNITAM meter and associated software allowed us to begin measuring time-shifted viewing for the first time in Ireland in September 2010. The Nielsen TAM system now measures and reports on Live viewing, VOSDAL viewing (viewed on same day as Live) and Consolidated viewing, which includes Live, VOSDAL and any viewing that takes place within 7 days of original broadcast. Programmes or commercials viewed in fast forward mode are not counted as viewing.

Ireland was amongst the earliest countries to have the capacity of measuring such trends in viewing behaviour.