Disclosure Avoidance Techniques Used for the 1970 through 2010 Decennial Censuses of Population and Housing

The U.S. Census Bureau’s disclosure avoidance (DA) methods have evolved over the past 50 years. The 2020 Census will be the first census protected by a formally private disclosure avoidance system based on differentially privacy methods. This paper summarizes the historical methods the agency used from the 1970 to the 2010 censuses, leading up to the adoption of the modernized disclosure avoidance methods.

This history discusses only publicly available information about the confidentiality protection methods as noted in official documentation of the relevant decennial censuses. All of the information in this summary was taken from historical public sources, except as noted. None of the information in this paper is confidential.

There is no public documentation of the disclosure avoidance methods used in the 1970 Census. This paper relies on an internal Census Bureau planning paper, now cleared for release, that provided a brief description of 1970 methods while highlighting options for disclosure avoidance for the 1980 Census (Zeisset, 1978). There is no information about 1970 methods in the 1970 Technical Documentation nor the 1970 Data User’s Guide. Likewise, no documentation of disclosure avoidance was found in public or internal papers for pre‐1970 censuses.