USA: DVRs shift viewing habits, and ratings

The increasing usage of digital video recorders, which easily allow viewers to postpone watching their favorite shows, has vastly complicated the math of TV ratings, new Nielsen data show.

And it explains how ABC's Modern Family ultimately eclipsed Fox's American Idol among key young-adult audiences.

In final season rankings out Monday (Nielsen's time-shifted rankings are delayed by about two weeks),Family, already one of TV's top shows, added an average of nearly 5 million viewers in the seven days after new Wednesday episodes aired against Idol. That's the biggest gain for any series, for a total of 16.7 million viewers.

Among viewers ages 18 to 49, the comedy jumped 48% when factoring in delayed viewing, while Idol's performance show gained just 17%.

But viewers rarely delay reality shows, news, awards telecasts and sports programming by more than a day. Sitcoms and dramas are most prone to procrastination, accounting for 29 of the top 30 gainers.

Nielsen says 44% of homes now have DVRs, and though the adoption rate has slowed recently, those who have the devices are using them more often. Just 47% of viewing by young-adult DVR users was live, down from 61% four years earlier.