The Great White Whale of media studies -- Nieslen keeps the whole of their data close to their vest, but you can get at in pieces. Here are some common places to find Nielsen ratings:
year in review summary, broadcasting statistics, prime-time Nielsen rankings for the year, who's-who, corporate histories of the networks, AND MORE! (previous years in Main Library)
Print & Online.
Microfilm (1905 - 2016)
Print (1975 - present)
Online Full-Text (1905-2000) in Entertainment Industry Magazine Archive
Online Selected Articles (2000 - present) in Performing Arts Periodicals Database
Nearly every issue includes weekly reports for Nielsen Ratings and Domestic & International Boxoffice Grosses . You can also find Variety (beginning-2000) in Entertainment Industry Magazine Archive database