NEW YORK — IT surely wasn’t what CBS dreamed about when Katie Couric was hired: the CBS Evening News last week recorded its smallest audience since 1987, and probably many years before that.It also didn’t help that the average of 6.05 million viewers came at the beginning of the important May ratings “sweeps”.

Meanwhile, ABC’s World News recorded its widest advantage in viewership over NBC’s Nightly News since the week Peter Jennings died in August 2005.

The victory, ABC’s ninth in 13 weeks over NBC, adds to the sense that Charles Gibson is eclipsing Brian Williams as the nation’s favourite network news anchor>

World News averaged 8.1 million viewers last week (5.7 rating, 12 share). NBC’s Nightly News had 7.5 million viewers, its fourth-lowest figure since at least 1987 (5.3, 12), and CBS had a 4.3 rating and 9 share. The year 1987 is a benchmark because that’s when Nielsen began using its “people meter” technology.

Those are worrisome numbers for networks heading forward, since news viewership normally drops off in the summer. Major news events, of course, could dramatically change things.

In prime time, Fox found itself in an unusual position whilI>American Idol <$>is airing — third place in viewership. CBS won, while ABC recorded its best non-Oscar week since last fall, helped by the two-hour Grey’s Anatomy special last Thursday.