Methodology of the Social Explorer Population Projections
2. Cohort Component Method
2.1 The aim
This project aims to project the population of states, counties and census tracts by age, sex and race including: White alone, Black or African-American Alone, American-Indian and Alaska-Native Alone, Asian Alone, Native-Hawaiian and Other Pacific Islander Alone, Some Other Race Alone, Two or More Races.
The cohort component technique uses demographic change to project population growth. The technique projects the population by age groups, in addition to other demographic attributes such as sex and ethnicity. The processes or stages of the projection tool are summarized in the following equation:
Pt+n=survived population+births+net migrants
In order to project population, the number of survived people needs to be found as well as the number of births and migrations that occurred during the specific period. Add these numbers and you will get population for a desired year.
When the cohort component model is used as a projection method, it assumes that components of demographic change, mortality, fertility and migration will remain constant throughout the projection period.