Fig. 1.

Nationwide migration at the county level. Notes: Outflow is the number of people who were residents of a county in the previous month, who on a given date in the current month have a different modal night county. The population change fraction is this number divided by the total number of residents of that county who were in the data on that date. Inflow counts the number of people who were not residents in a county in the previous month, who have the county as their modal night county on a given date. Net flow is inflow minus outflow. All measures are averaged across the last week of the month.