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, gender, 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 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. Slightly modified county population estimates, which only affect estimates for the state of Hawaii and hurricane Katrina-impacted counties/parishes, are used in SEER*Stat software and available for download as text files.
U.S. Census Tract Population Data
The 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.