Fig. 1.

Design for quantifying and studying localized population movement using cellphone data. Notes: Panel (A): Cellphone location data is gathered passively and used to measure population movement by origin county and day. Intersecting circles indicate social proximity. Data is gathered on timing of shelter-in-place ordinances. Study assesses change in travel patterns which indicate social distancing (reduced social contact). Panel (B): Variation in cellphone-derived movement data over study period (February 23 to May 1, 2020). Base rate for daily movement after March 8 (onset of COVID-19 in United States) is history of day-of-week movement data collected in prior periods. Local polynomial regression indicates 25% decline (national average) in movement during study period.