Locating Sales Numbers Online
Most recording industry information regarding sales is proprietary and difficult to find in any detail. An effective way to find some of this information is in books about music history, performer-related biographies, bibliographies, and discographies.
Finding Sales Numbers in Print
The Loeb Music Library has a selection of key sources available in the Aldrich Reading Room, including many of Joel Whitburn's Billboard chart compilations.
The Baker Library at the Harvard Business School owns both current and historical sources, such as:
- Print and online publications from the International Federation of the Phonographic Industry (IFPI).
- Record Retailing Yearbook. New York: M & N Harrison,  Baker Business; Historical Collections -- Baker Old Class; Call Number: SVSK R31
- Hung, Michele and Esteban Garcia Morencos, ed and comp. World Record Sales, 1969-1990: A Statistical History of the World Recording Industry. London: IFPI, 1990. Baker Business; Stacks -- LC Books; Call Number: HD9697.P562 W67 1990
Find out who owns the publishing rights for a song (and sometimes who has recorded it) by searching the databases maintained by these performing rights organizations. Since they all license different music, it's important to check all three.