US television ratings provider Nielsen Media Research has broken through the 'top ten' barrier with its portable people meter.

The company has just rolled out the measurement system in the city of Atlanta - where it is expected to highlight the same dramatic changes in TV ratings that have been evident since it was first introduced for local ratings in Boston in 2002.

The people meter, now employed in the nation's top ten media markets, has shown a sharp rise in TV viewing by children and young adults and a modest decline in viewing by older people.

In Detroit last month, figures for the prime target 18-34 age group watching breakfast TV nearly doubled from a year earlier, when Nielsen was still using its long-standing paper diaries in the city.

The trend is the same throughout the other major centers where people meters are in operation. The devices electronically record the viewing habits of each household member, making it easier for marketers to decide where to put their ad dollars.

Nielsen says the meters are showing higher viewing in the 18-34 group because younger people tend to be too busy to fill out paper diaries as conscientiously as older viewers.

The latter, however, sometimes note a full length show in diaries even if they tuned-in only briefly, thus explaining the decline in their viewing hours shown up by the more finely tuned meters.

Data sourced from Wall Street Journal Online; additional content by WARC staff