The NCI procures and maintains U.S. population data for the denominators of cancer incidence and mortality rates. Annual mid-year population estimates stratified by age, sex, bridged race, and Hispanic ethnicity are available at county and census tract levels. These are also referred to as "July 1st Populations," which have incorporated migration data and represent average populations in a year. They differ from "April 1st populations" published by the Census Bureau, which are solely based on information collected in the Decennial Censuses and represent a snapshot of the U.S. as of April 1st.

U.S. County Population Data

The bridged race county population estimates are produced under a collaborative arrangement between the U. S. Census Bureau and the National Center for Health Statistics with support from NCI through an interagency agreement, except for 2010-2019 intercensal population estimates that are produced by Woods & Poole Economics, Inc. through a contract with NCI. Slightly modified county population estimates, which only affect estimates for the state of Hawaii, are used in SEER*Stat software and available for download as text files.

Impact of Revisions on 2020 U.S. Population Estimates

In the April 2025 data release, the NCI used bridged race population estimates derived from revised 2020 Census estimates. These estimates reflect minor changes in population estimates for years 2022 and earlier, compared to those released in April 2024, which marked the first year the 2020 Census data were incorporated. While the new estimates are not significantly different overall compared to prior estimates, there are small differences in populations by age and smaller areas largely due to the incorporation of Hispanic origin data from the 2020 Census for the first time.

U.S. Census Tract Population Data

The bridged race census tract population estimates are produced by Woods & Poole Economics, Inc. (W&P) with support from NCI through a contract with methodology jointly developed by NCI, W&P, and the North American Association of Central Cancer Registries (NAACCR). Text data files and SEER*Stat databases are available for download to anyone who requests them and agrees to certain standard data use conditions.