Those figures are among the 18-to-49-year-old viewers who draw the most advertising dollars to the show. The results point to the kind of erosion that eventually affects just about every long-running show on television.

Initially, “Idol” appeared to have been beaten — narrowly — in the 8 to 8:30 p.m. half-hour by the CBS comedy hit “The Big Bang Theory,” which had a 5.2 rating in that 18-49 audience compared to a 5.1 for “Idol.” But adjusted national numbers indicated that the show had actually tied “Big Bang” with a 5.2 for the half-hour.

Those numbers were further adjusted Friday afternoon and showed “Big Bang” had indeed edged ahead with a 5.3 to a 5.2. The win was significant because no previous CBS entertainment show has finished ahead of “Idol” in those 18-49 viewers.

“Idol” scored a 6.3 rating for its second half-hour and averaged a 5.7 rating in the 18-49 measure for the full 8 to 9 p.m. hour, down from a 7.8 last year. That is a worse percentage falloff  than the show experienced on Wednesday night, and it may be a signal that viewers will not latch on to the series this year as they have in the past. Perhaps most telling, two years ago on its second night of the season, “Idol” had a 10.1 rating.

In terms of total viewers, “Idol” was down a bit less, 21 percent from last year. It averaged 18 million on Thursday, down from 22.9 million a year ago.

By any standard, “Idol” remains a hit, but its power is clearly diminished. One effect can be seen in the 9 p.m. hour on Thursday, when “Idol” was not able to help a new drama, “The Finder.” The Fox network easily won the 8 p.m. hour with “Idol,” but it fell to last place in the 9 p.m. hour.

In my opinion Season 8 was the best Idol ever, Adam Lambert was Outstanding and should have been the winner, on the other hand he is a winner. No American Idol For Me.