The Big Bang Theory finished ahead of Fox behemoth American Idol in the key 18-49 ratings demographic last night. Idol, now in its eleventh season, dominated the night's ratings, despite a year to year decline of around 25% in its ratings.

The 100th episode of The Big Bang Theory was watched by 15.83 million people, down only marginally from last week's audience of 16.13 million viewers. The Big Bang Theory finished second, behind Idol, in total viewers and households.

In the important 18-49 demographic, Big Bang beat American Idol in the same half-hour period with a 5.3/15 rating to Idol's 5.2/15. Idol's 18-49 rating rose to 5.7/15 for the 8 o'clock hour as a whole. Both Big Bang and Idol were adjusted up a tenth of a rating point in the final ratings. The Big Bang Theory matched its 18-49 rating from last week, seemingly unhurt by the return of the popular reality show. The Big Bang Theory was the night's most-watched and highest-rated scripted program. American Idol was the top show of the night overall.