For the third week in a row, Jay Leno's Tonight Show adults 18-49 weekly ratings average has tracked at exactly the ratings of Conan O'Brien's Tonight Show in the same week of each show's run.
David Letterman's Late Show was in original episodes last week (April 19-23), and he picked up a tenth of a point in the adults 18-49 ratings vs. the previous week which was repeats, but was again beaten by the Tonight Show as he has been each week since Jay returned.
For the week, while Jay's Tonight Show adults 18-49 overall average was a 1.0 rating and Letterman's ratings average was a 0.9, the adults 18-49 viewership difference was somewhat wider than those numbers would indicate (1.361m for Leno, 1.132m for Letterman).
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For historical reference, here are last season’s season-to-date averages through April 24, 2009:
11:35 p.m. ET
NBC “Tonight,” 1.4/6
CBS “Late Show,” 1.1/4
ABC “Nightline,” 1.1/4