U.S. Population Change Map 2010-2020

2 minute read

I was recently thinking that now that the U.S Census Bureau completed the 2020 census that it would be interesting to compare population differences between 2010 and 2020.

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The U.S. Census published a blog post last August that covers this. They include a map of Percent Change in County Population between 2010 and 2020. I think percent change is a great choice for the unit of measure of change. I wanted to do something similar but do it in a GIS so I could zoom in and out of the map, inspect the different county names, and manipulate the tables. I also wanted to make a quick web map.

I didn’t spend the extra time to add a legend, but blue means high population growth and red means population decline. You can hover over different counties and see the pop-ups with their attributes. There are two map layers that can be toggled on and off. Population difference is the change in person count per county from 2010-2020. Population difference per sq km normalizes the population change by the number of square kilometers of land area per county. For the symbology classes, there are 25 classes using a quantile classification, therefore each class contains an equal number of values.

When making my map I had a hard time finding the data on census.gov. The census blog post I read used the 2010 and 2020 Census Redistricting Data as sources. However, when I went to the summary file page. I felt that I really didn’t want to deal with reading all the documentation or figure out how to deal with the legacy files. Neither did I want to use Microsoft Access, SAS, or R. Fortunately my friend Jason Shapiro let me know about IPUMS NHGIS (https://www.nhgis.org/), National Historical Geographic Information System (NHGIS) provides free online access to summary statistics and GIS files for U.S. censuses and other nationwide surveys from 1790 through the present. After creating an account, I was able to get both my GIS files and population statistical data. Then I did the table join with QGIS. I also used the QGIS2Web plug-in to make a web map, that I was able to deploy to my site after a few tweaks.

Another motivation for the project is to combine the population growth data with residential real estate prices, to find out high value real estate markets. I found some great data from the Redfin Data Center and was able to integrate it with my Census data. I might publish these results in future blog post.