NOTE: This posting has been updated with the slightly higher final ratings results for the premiere show of The Jay Leno Show.

After a long wait and even more publicity The Jay Leno Show premiered last night, attracting a considerable audience of 18.42 million viewers and  nabbing a respectable 5.3 rating in the 18-49 demographic. Of course the question remains about how the show will perform in the long term.

The Tonight Show with Conan O’Brien had a premiere night audience of 7.1 million viewers. The premiere week average was 6.1 million and the season-to-date average for Conan’s two month tenure is around 1.2 million (60.6% less than the premiere night). Based on these relative drop-offs The Jay Leno Show can be expected to averaging just over 7 million viewers within two months.

Utilizing the same formulas for relative drop-offs in the more important 18-49 demographic, The Jay Leno Show would be getting a 1.8 rating for that demo.

Of course there are many other factors that might lead to the show maintaining more or less viewers. The premiere of The Jay Leno Show may have been buoyed by its large promotional campaign, and by general curiosity about its format, so it might experience a bigger drop off than Conan. The competition at 10:00 p.m. might turn out to be stronger than in the late night period, leading to further ratings erosion. Or, perhaps Jay Leno will turn out to draw big audiences more consistently once the premiere weeks for the Fall season finish.

Assuming the show does make a rating of 1.6 in the 18-49 demo, it would still be below the season average for most shows that were in the 10:00 p.m. time slot last year.

However, The Jay Leno Show is estimated to have a cost one-fifth as much as most network dramas, hence a lower hurdle rate. Jeff Zucker has said that an 18-49 rating of 1.8 would be a “home run” for The Jay Leno Show. If my predicted rating of 1.7 turns out to be accurate, it should be more than enough to keep the show on the schedule.