Behold an astounding season which not only ABC claimed the top 6 places in the yearly Nielsen register, but they were all sitcoms! A wave of fantasy and nostalgia comprised these entries, along with two failed clunkers riding on the winning coattails of the network leaders. Elsewhere, 2nd place CBS held tight to their early-mid 70's social relevance sitcoms and had to bid adieu to former 1st Place champ after 9 seasons. NBC found its next hit with Different Strokes, albeit the show was the only fare to write home about as the network was iced in 3rd place.Prior to September 2, TV Ratings Guide only had full access to ratings post-1984 and unearthed a treasure trove of data spanning back to 1964. Odd years, including 1978-79 have complete data intact, thanks to historic online newspaper articles. TVRG continues its mission to create a unified source for Historic Ratings before the internet created a prolific source of information. TVRG now possesses a conglomeration of elite ratings data; enjoy a view back into another era of Nielsen hstory.
ABC held an embarrassment of Nielsen riches in sitcoms (lest not underscore the word "embarrassment" with The Ropers and several failed sitcoms). They held a record 17 original sitcom entries and held room to pare down the roster. Successful entries such as Taxi and Mork and Mindy allowed ABC to part with What's Happening and Welcome Back, Cotter in the midst of another successful season. CBS also delivered a healthy roster of 15 sitcom entries, though 7 survived to the next season. Veterans All in the Family, Good Times and Rhoda ended durable runs, and Stockard Channing's Grease fame was not enough to sustain a Nielsen hit.
NBC made a valiant effort to resurrect their decimated sitcom schedule after cancelling all helpings the previous season. Diff'rent Strokes took off amid controversy over a blended cast, and tie-in Hello, Larry piggybacked via a 2-episode crossover. The remains sans BJ and the Bear were dispensed, and the network's prospects for improvement were far from sight.
Source -- http://www.americanradiohistory.com/Archive-BC/BC-1979/BC-1979-06-18.pdf