David Michael Letterman (born April 12, 1947) is an American television host, comedian, writer, and producer. He hosted a late night television talk show for 33 years, beginning with the February 1, 1982, debut of Late Night with David Letterman on NBC, and ending with the May 20, 2015, broadcast of Late Show with David Letterman on CBS. In total, Letterman hosted 6,028 episodes of Late Night and Late Show, surpassing friend and mentor Johnny Carson as the longest-serving late night talk show host in American television history. In 1996 Letterman was ranked 45th on TV Guide's 50 Greatest TV Stars of All Time.
Popularity
In 1975, encouraged by his then-wife Michelle and several of his Sigma Chi fraternity brothers, Letterman moved to Los Angeles, with hope of becoming a comedy writer. He and Michelle packed their belongings in his pickup truck and headed west. As of 2012, he still owned the truck. In Los Angeles, he began performing comedy at The Comedy Store. Jimmie Walker saw him on stage; with an endorsement from George Miller, Letterman joined a group of comedians whom Walker hired to write jokes for his stand-up act, a group that at various times would also include Jay Leno, Paul Mooney, Robert Schimmel, Richard Jeni, Louie Anderson, Elayne Boosler, Byron Allen, Jack Handey, and Steve Oedekerk.  By the summer of 1977, Letterman was a writer and regular on the six-week summer series The Starland Vocal Band Show, broadcast on CBS. He hosted a 1977 pilot for a game show entitled The Riddlers (that was never picked up), and co-starred in the Barry Levinson-produced comedy special Peeping Times that aired in January 1978. Later that year, Letterman was a cast member on Mary Tyler Moore's variety show, Mary. Letterman made a guest appearance on Mork & Mindy (as a parody of EST leader Werner Erhard) and appearances on game shows such as The $20,000 Pyramid, The Gong Show, Hollywood Squares, Password Plus and Liar's Club, as well as the Canadian cooking show Celebrity Cooks (November 1977), talk shows such as 90 Minutes Live (February 24 and April 14, 1978), and The Mike Douglas Show (April 3, 1979 and February 7, 1980). He was also screen tested for the lead role in the 1980 film Airplane!, a role that eventually went to Robert Hays.  His dry, sarcastic humor caught the attention of scouts for The Tonight Show Starring Johnny Carson, and Letterman was soon a regular guest on the show. Letterman became a favorite of Carson and was a regular guest host for the show beginning in 1978. Letterman credits Carson as the person who influenced his career the most.  NBC kept Letterman under contract to try him in a different time slot. Late Night with David Letterman debuted February 1, 1982; the first guest on the first show was Bill Murray. Murray later went on to become one of Letterman's most recurrent guests, guesting on the show's 30th anniversary episode, which aired January 31, 2012 and on the very last show, which aired May 20, 2015. The show ran Monday through Thursday at 12:30 a.m. Eastern Time, immediately following The Tonight Show Starring Johnny Carson (a Friday night broadcast was added in June 1987). It was seen as being edgy and unpredictable, and soon developed a cult following (particularly among college students). Letterman's reputation as an acerbic interviewer was borne out in verbal sparring matches with Cher (who even called him an asshole on the show), Shirley MacLaine, Charles Grodin, and Madonna. The show also featured comedy segments and running characters, in a style heavily influenced by the 1950s and 1960s programs of Steve Allen.  The show often featured quirky, genre-mocking regular features, including "Stupid Pet Tricks" (which had its origins on Letterman's morning show), Stupid Human Tricks, dropping various objects off the roof of a five-story building, demonstrations of unorthodox clothing (such as suits made of Alka-Seltzer, Velcro and suet), a recurring Top 10 list, the Monkey-Cam (and the Audience Cam), a facetious letter-answering segment, several "Film[s] by My Dog Bob" in which a camera was mounted on Letterman's own dog (often with comic results) and Small Town News, all of which would eventually move with Letterman to CBS.  Other memorable moments included Letterman using a bullhorn to interrupt a live interview on The Today Show, announcing that he was the NBC News president and that he was not wearing any pants; walking across the hall to Studio 6B, at the time the news studio for WNBC-TV, and interrupting Al Roker's weather segments during Live at Five; and staging "elevator races", complete with commentary by NBC Sports' Bob Costas. In one infamous appearance, in 1982, Andy Kaufman (who was already wearing a neck brace) appeared with professional wrestler Jerry Lawler, who slapped and knocked the comedian to the ground (though Lawler and Kaufman's friend Bob Zmuda later revealed that the event was staged).  The main competitor of the Late Show was NBC's The Tonight Show, which was hosted by Jay Leno for 22 years, but from June 1, 2009, to January 22, 2010, was hosted by Conan O'Brien. In 1993 and 1994, the Late Show consistently gained higher ratings than The Tonight Show. But in 1995, ratings dipped and Leno's show consistently beat Letterman's in the ratings from the time that Hugh Grant came on Leno's show after Grant's arrest for soliciting a prostitute;  Leno typically attracted about five million nightly viewers between 1999 and 2009. The Late Show lost nearly half its audience during its competition with Leno, attracting 7.1 million viewers nightly in its 1993-94 season and about 3.8 million per night as of Leno's departure in 2009. In the final months of his first stint as host of The Tonight Show, Leno beat Letterman in the ratings by a 1.3 million viewer margin (5.2 million to 3.9 million), and Nightline and the Late Show were virtually tied. Once O'Brien took over Tonight, however, Letterman closed the gap in the ratings. O'Brien initially drove the median age of Tonight Show viewers from 55 to 45, with most older viewers opting to watch the Late Show instead. Following Leno's return to The Tonight Show, however, Leno regained his lead.  Letterman's shows have garnered both critical and industry praise, receiving 67 Emmy Award nominations, winning 12 times in his first 20 years in late night television. From 1993 to 2009, Letterman ranked higher than Leno in the annual Harris Poll of Nation's Favorite TV Personality 12 times. For example, in 2003 and 2004 Letterman ranked second in that poll, behind only Oprah Winfrey, a year that Leno was ranked fifth. Leno was higher than Letterman on that poll three times during the same period, in 1998, 2007, and 2008.

Q: Was Letterman really popular
A: In 1993 and 1994, the Late Show consistently gained higher ratings than The Tonight Show.
How many viewers did he have
Letterman in the ratings by a 1.3 million viewer margin (5.2 million to 3.9 million),
Letterman in the ratings by a 1.3 million viewer margin (5.2 million to 3.9 million),