By: Emily Harris
In August 2021, the Census Bureau released the 2020 Census Redistricting data, providing county population totals (among other data points) for April 1, 2020. This data enabled us to revise the Utah Population Committee (UPC) 2010-2019 postcensal population estimates to create intercensal estimates. You can download the new set of intercensal estimates here. It is standard practice to revise postcensal estimates, benchmarked off the previous (2010) census, to terminate at the subsequent (2020) census counts. This process provides a continuous estimate series across Decennial time points.
Intercensal estimates are considered more accurate than postcensal estimates since they incorporate more definitive population data. Additionally, many organizations that use population estimates as denominators will either revise their previous work with the intercensal estimates (for calculating demographic and disease incidence rates) or incorporate them into historical series for products like projections and forecasts. A historical intercensal estimate series (1940-2009) created by the Utah Population Estimate Committee can be accessed here, and you can read more about different population estimates and their uses here.
Once we have the definite population count for the end/beginning of a decade (a new Census count), we can adjust the population estimates between the two census points to better reflect the decadal trend. This graphic, created by the masterful Pamela Perlich, beautifully summarizes the concept of intercensal estimates, postcensal estimates, and projections.
It’s important to note that our intercensal estimate adjustments do not impact the original postcensal births, deaths, or natural increase since these are administrative data and not estimates. As a result, net migration is the component of change where differences can appear between postcensal and intercensal estimates.
Now that the 2010-2019 intercensal estimates are complete, the UPC will create new postcensal estimates until the end of the decade. Then the cycle of adjusting 2020-2029 postcensal estimates to intercensal estimates will commence again.
Emily Harris is the senior demographer at the Kem C. Gardner Policy Institute.