Note: Both theand were in repeats in the latest week (May 31 - June 4). Unfortunately, I don't have easy access to information to compare the repeat status of the /Letterman weeks from 2009.
Jay Leno's1.0 adults 18-49 last week (May 31 -June 4) was even with the previous week, and one tenth of a ratings point below O'Brien's ratings trend, comparing the ratings for each show's fourteenth week. They've only been more than a tenth of a point apart once since the fifth week of each show's run.
Readers should note that 14 weeks into "(2009-10)" was the first week of September, 2009, as the broadcast TV year begins to show signs of life, but the 14th week of "Leno (2010-)" was the first full week of broadcast TV "summer" as things begin to slow down quickly.
/Letterman (2009-10) week 1 ended 6/5/09. Leno/Letterman (2010-) week 1 ended 3/5/10.
The/Letterman(2009-10) ratings do not include the final week the Tonight Show was in repeats prior to the Winter Olympics.
We have now passed Conan's 2009 start date (June 1). In another couple weeks, I will shift the start dates for the lines on the chart so that equivalent *calendar* dates line up, instead of the week sequence numbers. Or, I might just produce two charts each week, since it's little additional effort.