Three weeks back and three Leno ratings wins. Jay was steady last week, but Dave slipped a tenth of a ratings point. Note that the Thursday and Friday airings of Letterman's were pushed late by and were not included in the weekly average for the week ending 3/19.
For historical reference, here are last season's 18-49 season-to-date averages through March 20, 2009:
NBC “Tonight,” 1.4 adults 18-49
CBS “ ,” 1.1 adults 18-49 rating
And for additional historical reference, here is the tally of the adults 18-49 ratings for the entire run ofO'Brien's , except the final week of repeats prior to the Winter Olympics.