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Confidentiality

The Census Bureau has modified or suppressed some data on this site to protect confidentiality. Title 13 United States Code, Section 9, prohibits the Census Bureau from publishing results in which an individual's or business' data can be identified.

The Census Bureau's internal Disclosure Review Board sets the confidentiality rules for all data releases. A checklist approach is used to ensure that all potential risks to the confidentiality of the data are considered and addressed. For more information on how the Census Bureau protects the confidentiality of data, please explore the following links.

Questions about confidentiality may be addressed to: webmaster@census.gov Attention: Policy Office.

Title 13, United States Code: Title 13 of the United States Code authorizes the Census Bureau to conduct censuses and surveys. Section 9 of the same Title requires that any information collected from the public under the authority of Title 13 be maintained as confidential. Section 214 of Title 13 and Sections 3559 and 3571 of Title 18 of the United States Code provide for the imposition of penalties of up to five years in prison and up to $250,000 in fines for wrongful disclosure of confidential census information.

Disclosure Limitation: Disclosure limitation is the process for protecting the confidentiality of data. A disclosure of data occurs when someone can use published statistical information to identify either an individual or business that has provided information under a pledge of confidentiality. Using disclosure limitation procedures, the Census Bureau modifies or removes the characteristics that put confidential information at risk for disclosure. Although it may appear that a table shows information about a specific individual or business, the Census Bureau has taken steps to disguise or suppress the original data while making sure the results are still useful. The techniques used by the Census Bureau to protect confidentiality in tabulations vary, depending on the type of data.

Suppression: Suppression is a method of disclosure limitation used to protect individuals' confidentiality by not showing (suppressing) the cell values in tables of aggregate data for cases where only a few individuals or businesses are represented. The cells that are not shown are called primary suppressions. To make sure the primary suppressions cannot be closely estimated by subtracting the other cells in the table from the marginal totals, additional cells are also suppressed. These additional suppressed cells are called complementary or secondary suppressions. The process of suppression does not change the marginal totals, so the integrity of the data is not adversely affected. Before the Census Bureau releases data, computer programs check published tables for both primary and complementary disclosures. Suppression was used for the 1980 Census of Population and Housing and is now used for economic surveys and censuses.

Example -- With Disclosure

Value of Shipments
by County and Industry


Industry
County W X Y Z Total
   Alpha151*3*1*20
   Beta 2010101555
   Gamma 3*10102*25
   Delta121472*35
Total503530 20135

NOTE: * Indicates cells in which data may be identifiable due to the low number in the cell.


Example -- Without Disclosure, Protected by Suppression

Value of Shipments
by County and Industry


Industry
County W X Y Z Total
   Alpha15DDD20
   Beta 2010101555
   GammaDD10D25
   DeltaD14DD35
Total503530 20135

NOTE: D indicates data withheld to limit disclosure.

Data Swapping: Data swapping is a method of disclosure limitation designed to protect confidentiality in tables of frequency data (the number or percent of the population with certain characteristics). Data swapping is done by editing the source data or exchanging records for a sample of cases when creating a table. A sample of households is selected and matched on a set of selected key variables with households in neighboring geographic areas that have similar characteristics (such as the same number of adults and same number of children). Because the swap often occurs within a neighboring area, there is no effect on the marginal totals for the area or for totals that include data from multiple areas. Because of data swapping, users should not assume that tables with cells having a value of one or two reveal information about specific individuals. Data swapping procedures were first used in the 1990 Census, and will be used for Census 2000 and for the Census Bureau's new American Community Survey. For a description of the disclosure limitation procedures used in the economic census and surveys see the discussion on suppression.

Protection of Microdata Files: The Census Bureau sometimes releases microdata files which contain data from the censuses of the United States population and household surveys, which it conducts. These files contain individuals' responses that represent only samples of the population and have had all individual identifiers (such as name and address) removed from the records. In addition, to protect confidentiality, the Census Bureau may modify distinguishing characteristics (such as high levels of income), and restrict geographic identifiers (such as the name of a city) so that populations are composed of at least 100,000 people. This is done to protect the identity of individuals.


Source: U.S. Census Bureau.   Last Revised: July 28, 2003

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