NBC news viewership down

The truncated Fourth of July workweek ushered in an ignoble milestone for “NBC Nightly News,” as the once-dominant evening newscast recorded its lowest ratings since the advent of Nielsen Media’s people meter in 1987.

With anchor Brian Williams off for most of the week, the NBC newscast drew an average of only 6.84 million viewers last week, trailing for the 11th week in a row to ABC’s “World News With Charles Gibson,” which garnered 7.48 million viewers. Both beat “CBS Evening News With Katie Couric,” which attracted 5.62 million viewers. (The weekly averages do not include the July 4 holiday.)

This season NBC owns the top-rated evening news show, but it is fielding a strong challenge from ABC, the only network to have increased its audience this season.