The first week of "The Tonight Show with Conan O’Brien" walloped CBS’s "Late Show with David Letterman" in the key demographic of adults 18-49, according to final national Nielsen data released Thursday.

"Tonight" averaged a 2.3 rating/10 share in the demo, compared to a 0.9/4 for "Late Show," NBC said. That’s a 156 percent margin of victory, the biggest since May 1992 (the month of the Johnny Carson-Jay Leno transition).  Week one of O’Brien gave "Tonight" its best ratings in the demo since 2005.

“This is beyond our wildest expectations,” said Rick Ludwin, Executive Vice President, Late Night and Primetime Series, NBC Entertainment. “Conan has brought new younger viewers to 11:35 pm and we’re gratified that the demographic trend has continued here in week two, where the early numbers continue to show dominant victories, in all the key categories, for ‘The Tonight Show’.”

Letterman has closed the gap on O’Brien dramatically since O’Brien’s big premiere– but that’s among households, which don’t matter in modern TV. NBC believes O’Brien will continue to fare much better in demos and viewers than he appears to be doing in the overnights.

Indeed, O’Brien’s week one household margin of victory was 62 percent, compared to the 156 percent lead he had in the final demos.

Meanwhile, in those not-so-important overnight household numbers, "Tonight" retook the lead after falling behind on Tuesday. The numbers: "Tonight" 3.2/8, "Late Show," 3.1/8.   

–Josef Adalian

The full NBC press release on last week’s numbers follows:

UNIVERSAL CITY, Calif. – June 11, 2009 – Conan is the new King of Late Night. “The Tonight Show with Conan O’Brien” was the dominant winner in its first week on the air, delivering huge margins of victory in every ratings category.  “The Tonight Show with Conan O’Brien” won the week of June 1-5 with a 2.3 rating in the key measure of adults 18-49, the highest rated week for “The Tonight Show” in more than four years, and a towering 156 percent margin over CBS’s “Late Show with David Letterman” in adults 18-49.  Even excluding the highly rated premiere show on June 1, Conan won the week with a 1.9 rating among adults 18-49 and by 111 percent over the CBS program (0.9).

“This is beyond our wildest expectations,” said Rick Ludwin, Executive Vice President, Late Night and Primetime Series, NBC Entertainment. “Conan has brought new younger viewers to 11:35 pm and we’re gratified that the demographic trend has continued here in week two, where the early numbers continue to show dominant victories, in all the key categories, for ‘The Tonight Show’.”

Back in week one, the previously released metered-market household ratings had showed Conan dominating the week by a 62 percent margin; that lead over “Late Show” expanded to 156 percent in the key 18-49 category (2.3 vs. 0.9) and 267 percent in adults 18-34 (2.2 vs. 0.6), according to national ratings released today by Nielsen Media Research.  “The Tonight Show with Conan O’Brien” out-rated “Late Show” in every significant ratings category — adults, men and women 18-34, 18-49 and 25-54, plus total viewers — on all five nights of the week.

The 156 percent margin of victory in 18-49 is the highest for the “Tonight Show” over a full week of “Late Show” originals since at least May 1992.  Even excluding the high-rated Monday premiere, the 111 percent advantage on Tuesday through Friday is the best for “Tonight” over all "Late Show" originals in more than 10 years (since the week of February 15-20, 1999, 115 percent)
Conan’s 2.3 rating for the week in adults 18-49 is the highest for “Tonight” since the week of February 28-March 4, 2005.

Conan’s average rating for the week in the younger half of the key 18-49 demo, in adults 18-34, a 2.2, is a top-10 result among all primetime programs for the week of June 1-7, tying Fox’s “The Simpsons” for #10 on that list.

Conan’s ratings dominance helped lift “Late Night with Jimmy Fallon” at 12:35 a.m. ET to his highest weeklong 18-49 rating ever, a 1.0.  In 18-49 rating, Jimmy’s margin of victory over CBS’s “Late Late Show with Craig Ferguson” was a hefty 67 percent and that margin climbed to 125 percent in the younger half of the demo, adults 18-34 (0.9 vs. 0.4).  Jimmy even out-rated Letterman in 18-49 (1.0 vs. 0.9) for the week and dominated Letterman in 18-34 (0.9 vs. 0.6) despite airing an hour later than the CBS telecast.

Since his March 2 debut, Jimmy Fallon has finished #1 in the time period among the broadcast networks on 68 of 70 nights in adult 18-49 rating, including three ties. 
At 1:35 a.m. ET, “Last Call with Carson Daly” delivered its biggest 18-49 rating (0.6) since the week of October 15-19, 2007, and biggest overall audience (1.4 million) since the week of December 22-26.

Conan’s debut on Monday, June 1 generated a 3.8 rating in adults 18-49 and 9.2 million viewers overall, matching the top “Tonight” 18-49 rating on any night of the week since Monday, Jan. 24, 2005 (tying the night of the President Obama interview, Mach 19, 2009).  In total viewers, it’s the biggest Monday audience for “Tonight” since that January 24, 2005 telecast, a special tribute to Johnny Carson.