NBC’s Nightly News’ news demo tumbled 36% on Friday compared to the show’s Monday-through-Thursday average last week. ABC’s World News Tonight won the night in the demo, and in overall audience, after finishing behind NBC’s newscast each night, Monday through Thursday. The media, which has been covering the controversy about the show’s anchor Brian Williams, has been reporting today that it means viewers are abandoning Williams after he confessed he was not, as he had previously claimed, on a military helicopter that took a rocket propelled grenade in Iraq in ’03.

But Friday’s ratings also might suggest viewers care a lot less about this issue than does the media — particularly since NBC announced Friday afternoon it was launching an internal investigation into Williams’ claims about that helicopter ride and other claims he’s made over the years. Typically, viewers tune in to train wrecks — in this case, to see how Williams would handle himself on that evening’s newscast.

Broadcast evening news programs typically snag lower numbers on Fridays than earlier in the week, because people tend to consume less news heading into, and over, the weekend. ABC and CBS’ newscasts also clocked smaller numbers on Friday than they did earlier in the week. That may be why NBC News announced its internal investigation on Friday, and why Williams waited until Saturday to announce he was stepping down temporarily as anchor of the newscast.

Overall, the NBC newscast’s Friday audience was slightly lower than the previous two Fridays.  That day, Williams averaged 8.0 million total viewers, according to fast affiliate stats; the previous two Fridays his newscast averaged 8.1 million.  And, both stats are higher than Nightly’s season-to-date average for Fridays of 7.7 million viewers.

In total viewers, Friday’s ABC win is not unique — since David Muir took over the anchor chair on World News Tonight, ABC has clocked more viewers than NBC’s newscast a total of nine times to date, and six of them happened on a Friday.

Getting back to the news demo, which is the 25-54-year-old age bracket the news divisions sell to advertisers, Williams’ Friday looks to be low at 1.7 million viewers;  the previous four Fridays he averaged 1.9 million news demo viewers. The show’s season to date average on Fridays — 1.7 million news demo viewers.

Williams bigger drop this past Friday was his 40% slide among 18-49 year old viewers. If viewers are indeed turning away from Williams because of the controversy, that slide might reflect the rabid debate about Williams in social media.