A Special Census is a basic enumeration of population, housing units, group quarters, and transitory locations conducted by the U.S. Census Bureau at the request of a governmental unit. When local officials believe there has been a significant population change in their community due to growth or annexation, a Special Census may be in order. The assumption is that incorporating Special Census results would improve the population estimates for cities and towns. The goal is to include Special Census results for as many localities as possible. However, the Population Estimates Program maintains a set of requirements that Special Censuses must meet in order to be eligible for incorporation into the estimates. The purpose of these requirements is to stay true to the methodology we use to produce subcounty Population Estimates and to treat all areas fairly.

The Census Bureau may include Special Census results in the Population Estimates Program if the Special Census is of an entire governmental unit whose legal boundaries are identical to those used by the Population Estimates Program. Incorporating these results into the population estimates allows Census Bureau surveys—such as the American Community Survey—that rely on these estimates as statistical controls to also reflect the updated numbers. A complete list of Special Census results incorporated into the Population Estimates is summarized below.