NEW YORK: Primetime viewing figures for America's five biggest broadcast networks are down 6.6% year-on-year, despite an increase in "delayed viewing" via devices like digital video recorders, reports audience measurement specialist Nielsen Media Research.

Nielsen's data reveal that the five networks drew an average of nine million viewers to their primetime shows in the first two weeks of the latest season, which started in mid-September.

This figure, and the 6.6% decline, includes around 1.5 million viewers who watched back-recorded programs on DVRs in the seven days immediately following their original transmission.

When DVR playback figures are excluded, primetime viewer numbers fell 11.3% compared with the first four weeks of the same season in 2007.

In terms of "live" primetime viewing totals among the 18–49 age group, ABC's figures were down by 15.4% year-on-year, NBC by 14.5%, Fox by 13.3% and CBS by 4.6%.

The CW Network was the only one of the five major broadcasters not to post a decline on this metric.

Nielsen estimates that 24.4% American viewing households own DVRs, up from 18.6% last year.

The fragmentation of viewing habits encouraged by set-top boxes and online video-on-demand could have further negative consequences on future figures, according to some observers.

Fox's head of scheduling and research, Preston Beckman, says: "If you train the audience to believe there's no urgency in watching anything, then sometimes you never watch it at all."

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