Arthur Charles Nielsen, Sr. (September 5, 1897-June 1, 1980) was an American market analyst of Danish descent. He was the founder of the eponymous ACNielsen company in 1923, and in doing so advanced the new field of marketing research. This involved (1) test marketing new products to determine their viability prior to costly mass marketing and production, and (2) measuring product sales at a random sample of stores to determine market share. Careful statistical sampling is crucial to validate this process. The techniques developed by Nielsen were especially important for the efficient operation of a market prior to the introduction of computerized digital networks that in the 1990s enabled continuous and comprehensive monitoring of sales by product retailers. Nielsen was also a pioneer in developing methods of measuring the audience of radio and television broadcasting programs, most notably the Nielsen Ratings.

Nielsen inaugurated a National Radio Index for broadcasters and advertisers in 1942, followed by a television ratings service in 1950. By the time of his death, the company's revenue was US$ 398 million annually blank">http://www.time.com/time/magazine/article/0,9171,924209,00.html.

Nielsen was an alumnus of the _University of Wisconsin-Madison and a member of the Sigma Phi Society. He was captain of their varsity tennis team from 1916 to 1918 and a long time supporter of the game. Together with his son Arthur Junior, he won the U.S. Father and Son doubles title in 1946 and 1948. He was elected to the International Tennis Hall of Fame in 1971. The university awarded him an honorary Doctor of Science (ScD) in 1974.

In 1990, the A.C. Nielsen family made a generous donation to the University of Wisconsin-Madison to create a full-time MBA program specializing in marketing research. The program is the only full-time marketing research program in the United States.