The networks’ top evening TV programs suffered serious viewership ratings losses in the past few weeks, with several shows reaching record lows, USA Today reports.

However, there is more to the story. . . .

First, the losses. The Nielsen ratings showed that programs such as Lost, Desperate Housewives, ER, My Name Is Earl, The Simpsons, Two and a Half Men, CSI: Miami and Heroes had their worst ratings ever. "Still others," USA Today notes, "such as 24, Law & Order: Special Victims Unit and American Idol, had their worst ratings in two years or more."

Although ratings are down, viewership has held fairly steady. What is happening is that increasing numbers of people are watching the programs later on DVRs. USA Today reports:

"If you look at live plus seven-day viewing, those declines for several shows start to vanish," says Fox’s Preston Beckman. Lost lost 14% of its live viewing this season, but when time-shifting is factored in, the show is down only 1%. The Office, down 10%, is actually up 2% with delayed viewing included.

Advertisers, however, don’t pay for viewers watching on DVRs, because they believe—undoubtedly correctly—that such viewers regularly skip commercials. As a result, Nielsen is taking steps to measure the viewing of commercials.

In any case, although it is incorrect to cite the ratings numbers as suggesting that the appeal of these popular programs has fallen, they do indeed indicate that the revenue structure if commercial television is crumbling rapidly.

Like most such trends, this will probably result in short-term misfortune for both producers and consumers of televised entertainment, but will probably bring long-term benefits for both.