Source: U.S. Bureau of the Census, County Population Estimates by Demographic Characteristics - Age, Sex, Race, and Hispanic Origin; updated annually for states and counties. http://www.census.gov/popest/counties/asrh/. 2000 Census of Population and Housing for places; updated every 10 years. http://factfinder.census.gov
These data are derived from estimates of the resident population of all U.S counties and county equivalents by single years of age (age 0, 1, 2,....85 and over) for July 1 of the reference year, for years since 2000, or for April 1 for 2000.
Scope and Methodology:
The 2000 data on age were derived from answers to a question that was asked of all people in Census 2000. The age of the person was usually derived from their date of birth information.
Estimates for states and counties for years after 2000 are developed using a cohort-component method whereby each component of population change - births, deaths, domestic migration, and international migration - is estimated separately for each birth cohort by sex, race, and Hispanic origin.