After a 2.8 household rating in the preliminary metered markets for premiere of Conan on TBS, his second night fell 25% to a 2.1 household rating (i.e. 2.1% of US TV households on average watched the show) in Nielsen’s metered market overnight data. These are not the adults 18-49 ratings we typically report on the site. We'll have viewership and adults 18-49 (and perhaps other) demo group ratings later today.
If his adults 18-49 rating declines by a similar % it will be in the neighborhood of a 1.9 adults 18-49 rating.
Last night's other late night show's preliminary HH ratings:
Letterman's Late Night: 3.0, Leno's Tonight Show: 2.5, ABC's Nightline: 3.2