NEW YORK: Like three apartment-sharers soon to admit a fourth, US advertisers, agencies and TV companies are a-dither over the advent next month of a new rating system that monitors and reports upon the number of viewers that continue to watch a TV show during the ad breaks.

Right now, none of the trio can be certain how the advent of a fourth element will impact upon their present relationship.

Says Sara Erichson, general manager of national services at Nielsen Media Research - the begetter of the new ratings system: "This is a big change for the industry.

"There are some clients that want to move fast and some that want to take a more cautious approach. So many billions of dollars are spent on television advertising that a lot rides on making the right changes."

Few advertisers harbour doubts as to the desirability of the new system. Andrew Jung, Kellogg's senior director for advertising probably spoke for the majority of his peers when he told a recent conference: "Without this change I don't know how long television can be sustainable [for advertising]."

Nielsen already provides detailed data that analyze viewing second-by-second. It is used by agencies and TV networks to gather feedback on whether a given commercial works better in a given time slot.

However, the new dataset available to all comers as of May will measure the average rating for all commercials watched during a programme, rather than the popularity of individual ads.

Key information of this kind is commonplace elsewhere on the planet. In the UK, for example, BARB (Broadcasters' Audience Research Board) has provided minute-by-minute commercials viewing data for over twenty-five years.

Data sourced from Financial Times; additional content by WARC staff