Appendix 1 of Analysis of Apportionment Sensitivity to Population Miscounts

Alternate Apportionment Population Scenario

This appendix explains the methodology used to create the alternate population scenario by making adjustments to the 2020 population census using the Census Bureau’s “Post-Enumeration Survey” (PES) Report released in June of 2022.  This alternative population census will then be used to illustrate how relatively minor changes in the states’ population totals can impact the states’ House delegation sizes.

The 2020 population census is provided by the Census Bureau.1Census Bureau: Table 1. Apportionment Population and Number of Representatives by State: 2020 Census.  According to the Census Bureau, the apportionment population consists of the following three components:

  1. Household Households and Persons Per Household. (i.e., census count)
  2. Group New 2020 Census Results Show Group Quarters Population Increased Since 2010 (August 12, 2021) (e.g., college dormitories, prisons, nursing homes, etc.)
  3. Federally affiliated overseas Overseas Population for the 50 States – 2020 Census (military and federal workers)

The data for making the adjustments to the apportionment population totals is provided by the Census Bureau’s “2020 Post-Enumeration Survey Estimation Report”.5Census Bureau: Census Coverage Estimates for People in the United States by State and Census Operations.   Based on the statistical analysis conducted for the PES Report, only the first of these three components, Household Population (or census count) was said to be either overcounted or undercounted for each of the 50 states. (Read the PES Report for a full explanation of how their estimates were derived.) The data provided by the PES Report are shown in columns A and B of the table below.

The PES Report did not address the second two components (Group Quarters and Overseas Populations), so those items would remain unchanged.  Therefore, in order to utilize the PES estimates to adjust the 2020 apportionment population, its adjustments to the  Household Population totals will be added to, or subtracted from, the 2020 population census totals. These calculations are shown in the table on the following page, the columns of which are as follows:

Column A – Household Population (Census count) per the PES Report.
Column B – Percent over/(under) count per the PES Report.
Column C – Adjusted Census Count = A ÷ (1 + B)
Column D – Adjustment = C – A
Column E – Total 2020 Population Census by state per the Census Bureau.
Column F – Revised Apportionment Population = D + E (per this analysis).

For example, as shown in the table below, the PES Report estimated that Alabama’s Census Count of 4,896,000 (A) was undercounted by 1.05% (B).  Adding that undercount to the Census Count returns an adjusted census count of 4,947,954 (C), which is an increase of 51,954 (column D).  That increase is then added to Alabama’s 2020 apportionment population (column E) to arrive at an adjusted apportionment population (column F).

© [Published 07/14/22]

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