Differential Privacy Explainer
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October 2025
Protecting Individual Data Confidentiality; Preserving Accuracy
The U.S. Constitution gives Congress responsibility for overseeing a census of population every ten years, for the purpose of apportioning seats in the U.S. House of Representatives (Article I, sec. 2) and ensuring fair representation under the Fourteenth Amendment. To carry out this duty, Congress has enacted a set of laws collectively known as the “Census Act,” codified in Title 13, United States Code. A hallmark of our census taking is the strict confidentiality Title 13 requires for all data the U.S. Census Bureau collects.1 Significant research and experience — in the U.S. and around the world — show unequivocally that confidentiality protections are essential for convincing people that it is safe and beneficial to participate in the census. This trust is critical to ensuring a fair and accurate census. The Census Bureau approaches the confidentiality of personal and household responses in two ways:
- First, no one outside of the Census Bureau can access personal, identifiable census responses, for any reason — not law enforcement agencies (at any level of government), landlords, courts of law, or other federal agencies.2 Further, the law prohibits the use of census responses for any purpose other than tabulating anonymized statistics.
- Second, in order to secure the confidentiality of responses, the Census Bureau has adopted steps to ensure that the anonymous data it publishes at small geographic levels (such as block-level data for redistricting) will not allow re-identification of any person or household. It is that latter goal that has become more difficult in recent decades, with rapid advances in computer sciences and the growing volume and availability of other data sources that could make it possible to reconstruct the underlying information and identify individuals from even “anonymous” statistics.