Z on TV: Nielsen: Obama visit a big boost for Leno ratings - Sun critic David Zurawik writes about the business, culture and craziness of television - baltimoresun.com Last night's appearance by President Barack Obama was a ratings boon for The Tonight Show. The audience in metered overnight cities like Baltimore was the highest since Jan. 24, 2005, when the show featured a tribute to Johnny Carson, according to Nielsen figures released by NBC. The last time Tonight scored a higher overnight rating was on May 14, 1998 -- the night of the finale of Seinfeld when the cast appeared on Leno's program. Overnight ratings for last night's show were the fourth-highest in the 16-year history of Leno's show. Bottom line, one out of every four TVs in use last night was tuned to The Tonight Show. The overnight ratings from metered markets are not conclusive or final. But they generally match up when final figures are released. Here is the release from NBC: Last night's historic edition of "Tonight" matched the fourth highest metered-market household rating in the more than 16 years Jay Leno has been hosting "Tonight." President Obama's appearance last night is the first for a sitting U.S. President on a late-night talk show. Also appearing on last night's show was music superstar Garth Brooks. Last night's telecast of "Tonight" improved on the show's season-average 3.9 household rating in the metered markets by 187 percent. The other higher rated nights in the metered markets for "The Tonight Show with Jay Leno" are May 20, 1993, the night of the "Cheers" finale; May 25, 1992, the debut of "The Tonight Show with Jay Leno"; and May 14, 1998, the night of the "Seinfeld" finale.