After serving in the Army Corps. of Engineers during World War II, Nielsen joined his father's research firm, A.C. Nielsen, in 1945. He stayed with the firm for the rest of his adult life, becoming President in 1957 and Chairman in 1975.
Nielsen ratings are now synonymous with TV ratings, thanks largely to his use of cutting-edge technology -- he had the first general-purpose computer, the Univac, built back in 1948 -- which revolutionized the nascent business of market research.
Although it was A.C. Nielsen, Sr. who invented the first TV audience measurement system in 1950, under the son's tenure the Nielsen company became an international player in market research with revenues that grew from around $4 million per year to $680 million.
In line with the company's strict retirement policy, Nielsen stepped down as Chairman in 1983 and accepted the honorary title of Chairman Emeritus. He later orchestrated the sale of the company to the Dun & Bradstreet Corporation for $1.3 billion in stock.
Nielsen lived and died in Winnetka, Ill., where he was born on April 8, 1919. He is survived by his two sons and one daughter, a brother, two sisters and seven grandchildren.