FRED has recently added county-level data on net migration based on the American Community Survey. This survey asks whether the respondent has lived elsewhere in the previous year, and the responses are then extrapolated to represent migration flows across the U.S. The map shows the last year for which these data are available. What’s interesting about this picture is that there is no clear pattern. One could have expected, say, a hollowing out of the Midwest in favor of the coasts, but this does not appear to be the case. More-detailed analysis would likely illuminate some deeper patterns, but it looks like migration is largely regional in nature: Moves between neighboring counties, for example, create this random-looking patchwork.
How this graph was created: On GeoFRED, open the cogwheel, select geography “County” and search for “Migration.”
Suggested by Christian Zimmermann.