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WISH: Annual Population Estimates for Wisconsin Counties - Methods

Estimates from 2010 and after

These estimates were produced by the Population Division of the United States Census Bureau. The Population Estimates and Projections team provided estimates of the resident population for counties by demographic characteristics for Wisconsin from their Vintage 2022 estimates series. They were shared with the Department of Health Services for the purpose of generating health statistics.

The following passage from the Population Estimates and Projections Team explains why the estimates that land on a decennial year may be different than the results from the decennial Census:

"It is important to note that these estimates represent a tabulation from the 'blended base' for April 1, 2020 which integrates the results of the 2020 Census, the 2020 Demographic Analysis estimates, and the Vintage 2020 estimates series. Therefore, there may be differences between these April 1, 2020 estimates and the results released from the 2020 Census. The Vintage 2022 population estimates methodology statement is located at this URL."

Estimates from 1990 to 2009

The Office of Health Informatics (OHI) produced population estimates by sex and age group for Wisconsin counties and the state in non-Census years. The reference date for each set of annual estimates was July 1.

The estimates were produced through iterative proportional fitting, or "raking". The procedure adjusted a matrix of cells in an iterative fashion until the matrix converged with a separate set of marginal totals. The process continued until the internal cells converged with the totals for all dimensions (in this case, age group and sex) simultaneously. The term "raking" roughly describes how the matrix cells were distributed along each dimension until the matrix fit the marginal totals.

The data used to produce the estimates came from the U.S. Census Bureau and the Wisconsin Department of Administration. The Census Bureau's state age-by-sex estimates were used along with county total estimates and county estimates by sex by five-year age group projections from the Wisconsin Department of Administration's Demographic Services Center.

Last revised October 31, 2023