The first results of the 2020 population census are trickling in, and FRED is adding them to the database as the Census Bureau makes them available.

The FRED graph above shows the resident population for Jefferson County, Wisconsin; Prince George’s County, Maryland; and St. Louis City, Missouri (which is its own county).

The Census Bureau measures and adjusts the population data yearly from estimates about births, deaths, and migration. Again, these are just estimates. While births and deaths are well measured, migration is more difficult because there’s no U.S. requirement to register when you move, as there is for some countries.

The more precise population measurements come in the form of the decadal census, and this is the type of data FRED is receiving now. In the graph, do you see how population sometimes jumps up or down somewhat sharply? These are points in time when the new census data are added and the estimates for the previous years were a bit off. This doesn’t happen frequently, though. If you look at the full dataset, it’ll take some patience to find a handful of similar cases.

How this graph was created: Search for “resident population county” for your county of choice. From the “Edit Graph” panel, use the “Add Line” tab to search for other counties. Change units to 100 for 1970 and click on “Apply to all.”

Suggested by Christian Zimmermann.