NEW YORK (May 6) - The May "sweeps" is precisely the wrong time to hit low marks in the ratings. But several big shows did last week.

"American Idol" was seen by only 22.8 million people on Wednesday. While still enough to be the second most-watched show of the week (after Tuesday's "American Idol"), that's the smallest audience Fox's superhit has drawn for a regular night in more than two years, according to Nielsen Media Research.

"Idol" traditionally takes a ratings dip before the final shows. This year's competition is down to its final four singers.

CBS' "CSI: Crime Scene Investigation" had its second smallest audience ever for an original episode aired in its traditional Thursday time slot, Nielsen said. The previous week was the only one smaller.

The spinoff "CSI: Miami," seen by 13.9 million people on Monday, had the smallest audience in the series' history.

ABC's "Grey's Anatomy" struggled, too. While still a top 10 show with 15.3 million viewers, that was its smallest audience since moving into its Thursday time slot in fall 2006.

NBC wasn't immune, either. The Wednesday edition of "Deal or No Deal" reached its third smallest audience.

A hangover from the TV writers strike, viewers' increased reliance on digital video recorders and the onset of warm spring weather in daylight savings time are all possible culprits in television's depressing week.

CBS led the way, averaging 10 million viewers (6.5 rating, 11 share). Fox, with 9.4 million viewers (5.7, 10), won among the important 18-to-49-year-old demographic for the 17th straight week, the longest streak since NBC in 1996. ABC averaged 9.2 million viewers (6.0, 10), NBC had 6.5 million (4.3, 7), the CW 2.6 million (1.7, 3), My Network TV 1.2 million (0.8, 1) and ION Television 450,000 (0.3, 1).

Among the Spanish-language networks, Univision had 3.8 million viewers (1.9 rating, 3 share), Telemundo 1 million (0.6, 1), TeleFutura 680,000 (0.3, 1) and Azteca 150,000 (0.1, 0).

NBC's "Nightly News" won the evening news ratings race, averaging 8.2 million viewers (5.6 rating, 12 share). ABC's "World News" had 8 million (5.5, 12) and the "CBS Evening News" 5.8 million (4.1, 8).

A ratings point represents 1,128,000 households, or 1 percent of the nation's estimated 112.8 million TV homes. The share is the percentage of in-use televisions tuned to a given show.

For the week of April 28-May 4, the top 10 shows, their networks and viewerships: "American Idol" (Tuesday), Fox, 25.09 million; "American Idol" (Wednesday), 22.8 million; "Dancing With the Stars (Monday), ABC, 18.22 million; "CSI: Crime Scene Investigation," CBS, 18.01 million; "Dancing With the Stars" (Tuesday), ABC, 17.06 million; "Desperate Housewives," ABC, 16.76 million; "Grey's Anatomy," ABC, 15.31 million; "NCIS," CBS, 14.76 million; "House" (Monday), Fox, 14.64 million; "CSI: Miami," CBS, 13.88 million.

ABC is owned by The Walt Disney Co. CBS is a division of CBS Corp. Fox is a unit of News Corp. NBC is owned by General Electric Co. Telemundo is owned by General Electric. TeleFutura is a division of Univision. ION Television is owned by ION Media Networks.