This article explains what population projection data are, and answers questions about why these data are important, who is included in the data, and how the data are produced.
Population projections estimate populations at future dates. They help us answer questions about the predicted demographic makeup of a particular geography in the near future.
Population projections can be calculated at different geographic levels and for different racial or ethnic groups. Populations can also be projected out for any number of years. Projections are used not only in redistricting, but for academic research and planning purposes across a variety of sectors.
Census Block-level projections can be used to measure the impact of a proposed redistricting plan over a ten year period. A related use of Census Block-level population projections is in drawing districts that minimize demographic and total population changes between districts over a ten year period.
They may also be used in Racially Polarized Voting (RPV) litigation to predict what districts will look like in future elections.
Population projections used in redistricting include all residents of the US. Projections illustrate possible courses of population change based on a set of assumptions about future demographic trends, including births, deaths, net international migration, and domestic migration in any given geography. They rely on current or historical demographic data as the starting point from which to project future populations. Sources may include the US Decennial Census, the American Community Survey, immigration statistics, and other demographic surveys.
HaystaqDNA aggregated 2010 Census Block data up to the Block Group level. Then, they estimated rates of population change based on the racial and ethnic makeup of the Block group. Next, they used geocoded voter file and commercial file data to identify areas of new development, such as housing developments that did not exist during the 2010 census, and calculated a rate of change for those areas. Last, they disaggregated the population projections back down to the Block level.
The projections that the RDH hosts were produced by HaystaqDNA. They are available at the Census Block and Block Group levels. Population projections created by the US Census are at the state level. However, population growth is not uniform across states. In order to generate projections at the Block and Block Group level, it is necessary to estimate where in each state the population is changing.
We have projections based on the 2010 and 2020 decennial censuses, and populations are projected annually through 2030. The projection field names in the datasets correspond to variable names from either the P1 or P2 Table of the Census Summary Files. For descriptions of the field names, view the metadata for the dataset you are downloading.
The RDH purchased projections from HaystaqDNA and hosts them on our website. They are available at the Census Block level, for Census race categories and are projected until 2030.
Population projections can be found on the RDH website in each state’s data download page. They can be found by selecting “projections” in the “Filter by type of data” dropdown menu, or “HaystaqDNA” in the “Filter by source” dropdown menu.
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