NEW YORK — CBS' limited drama series "Under the Dome," the most popular show on television last week, is notable for what it's not: a rerun.

Three of the top 10 most-watched shows on TV last week were repeats, according to the Nielsen company. That number is an indication of how the summer television world has changed among the big networks.

During the corresponding week five years ago, six of the top 10 shows were reruns, Nielsen said. Go back a decade to 2003, and nine of the top 10 were programs that had aired before in colder-weather months.

Reruns used to be a dependable way for broadcasters to recoup the costs of making comedies and dramas. But with cable offering more original programs in summer, viewer tastes have changed. They increasingly don't want to see shows that have aired before, and networks are relying less on them.

The three reruns last week were all on CBS, which has an older and larger audience than their rivals. They include "NCIS" and "The Big Bang Theory," the top-rated drama and comedy during the regular season.

Besides "Under the Dome," CBS is also airing fresh episodes of the drama "Unforgettable" and viewers are responding. The NFL's Hall of Fame exhibition game and the nonfiction shows "America's Got Talent," "The Bachelorette" and "Big Brother" were all new programming that finished in the top 10.

Univision airs new telenovelas in prime time all summer, and viewers respond. The Spanish-speaking network easily beat Fox last week. Fox, weighed down by a low-rated soccer game on Saturday, had the smallest weekly audience of any of the major broadcasters this summer.

CBS easily won the week in prime-time, averaging 5.8 million viewers. NBC had 5.4 million viewers, ABC had 4 million, Univision had 3.1 million, Fox had 2.4 million, Telemundo had 1.5 million, ION Television had 1.2 million and the CW had 1.1 million.

USA was the most-watched cable network, averaging 2.6 million viewers in prime time. The Disney Channel had 2.4 million, TNT had 2.2 million, History had 2.1 million and Discovery had 1.9 million.

One week after beating NBC's "Nightly News" among the key 25-to-54-year-old demographic, ABC's "World News" fell back to second last week, by the slim margin of 68,000 people, Nielsen said.

Among all viewers, "Nightly News" averaged 7.5 million, "World News" had 7 million and the "CBS Evening News" had 5.8 million.

For the week of July 29-Aug. 4, the top 10 shows, their networks and viewerships: "Under the Dome," CBS, 11.41 million; "America's Got Talent" (Wednesday, 9 p.m.), NBC, 10.28 million; NFL Exhibition Football: Dallas vs. Miami, NBC, 10.11 million; "America's Got Talent" (Tuesday), NBC, 9.81 million; "Football Pregame," NBC, 8.9 million; "60 Minutes," CBS, 8.22 million; "The Big Bang Theory," CBS, 8.03 million; "The Bachelorette," ABC, 7.94 million; "NCIS," CBS, 7.66 million; "Big Brother 15" (Thursday), CBS, 7.12 million.