I'm not certain how the Tuesday Tonight Show pre-emption skews the year to year comparison*, but for only the second time since he returned Jay Leno's Tonight Show ratings were above those of Conan O'Brien's Tonight Show on a calendar week basis (2010 vs. 2009).
Leno's Tonight Show for the week of November 1-5 averaged a 1.0 rating with adults 18-49, while Conan's Tonight Show averaged a 0.9 adults 18-49 rating for the comparable calendar week last year (November 2-6, 2009).
Letterman's Late Show scored a 0.9 adults 18-49 rating last week.
*Note that due to the mid-term elections, Late Show Tuesday ratings were excluded from the averages and the Tonight Show was pre-empted Tuesday. No election effects last season.
Last season timing note: The Late Show staff member extortion story broke on October 1, 2009.
The chart shows the late night adults 18-49 weekly average ratings for 2009 and 2010.
Note: The week ending 7/2/2010, the Tonight Show was in repeats, and was delayed by Wimbledon coverage. The week of 7/9/2010 the Late Show was in repeats, and both shows Monday airings were excluded because of the holiday. For the weeks ending 7/16-8/6, Late Show was a repeat only on Friday. The week ending 8/13, Late Show was encores all week. Both Late Show and Tonight Show were repeats the week ending 8/20. For the week of 9/3/10, Late Show ratings were based on four days only. Note for the week of 9/10/10 NBC's Thursday telecasts were delayed by a primetime NFL overrun. Friday's "Late Show" was an encore, Monday results are excluded from these averages due to the Labor Day holiday. Late Show was in repeats the week of 9/17/10. Note that due to the mid-term elections, Late Show Tuesday ratings were excluded from the averages and the Tonight Show was pre-empted Tuesday the week of Nov 1-5.