Jay Leno's Tonight Show 1.1 adults 18-49 rating last week (May 10-14) was the same as the previous week, and was above the same rating as Conan O'Brien's Tonight Show in the eleventh week of each show's run. There has been little difference between the two show's ratings trends since week 5 of their run's.
Readers should note that 11 weeks into "Conan (2009-10)" was the second week of August, 2009, the absolute nadir of the broadcast TV year, but 10 weeks into "Leno (2010-)", is still during the regular broadcast season.
David Letterman's Late Show stayed even with a 0.9 adults 18-49 rating vs. the previous week, and was again beaten by the Tonight Show as it has been each week since Jay returned.
Conan/Letterman (2009-10) week 1 ended 6/5/09. Leno/Letterman (2010-) week 1 ended 3/5/10.
The Conan/Letterman(2009-10) ratings do not include the final week the Tonight Show was in repeats prior to the Winter Olympics.
For historical reference, here are last season’s season-to-date averages through May 16, 2009:
11:35 p.m. ET
NBC “Tonight,” 1.4/6
CBS “Late Show,” 1.1/4
ABC “Nightline,” 1.1/4