NBC boasted on Thursday that The Tonight Show with Jay Leno has beaten CBS's Late Show with David Letterman over the first 11 weeks of the current season by an average of 7 percent among the key demographic group of adults 18-49. Among that group, Tonight has averaged 1.26 million viewers, while Late Show has averaged 1.18 million. The result, it added, reverses the order of a year ago when Late Show led by 0.3 percent -- 1.353 million vs. 1.349 million. What appears striking about the figures, however, is the realizaiton that at this time a year ago, Tonight was hosted by Conan O'Brien and that Leno this season is attracting 7 percent fewer viewers in the key demo than O'Brien did. Among total adults, however, Leno is coming out ahead with 3.8 million viewers, 52 percent ahead of O'Brien's 2.5 million.