The US Centers and Disease Control and Prevention (CDC) tracked anonymized location data from mobile devices to find that mandatory stay-at-home orders can help reduce activities associated with the spread of COVID-19, including population movement and close person-to-person contact outside the household.
The publicly available data was obtained to estimate county-level raw data regarding movement. The analysis, latest to use personal devices and the data they generate to describe behaviors relevant to public health, estimated population movement by computing the percentage of individual mobile devices (for example, mobile phones, tablets, or smart watches) reporting each day that were completely at home (that is they had not moved beyond a 150-meter radius of its common nighttime location) within a given county, using a 7-day rolling average to smooth each county’s pre- and postorder time series values.
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“These findings can inform public policies to potentially slow the spread of COVID-19 and control other communicable diseases in the future,” notes the researchers who were from CDC Public Health Law Program, CDC COVID-19 Response Team, and Georgia Tech Research Institute, in the analysis recently published in CDC’s Morbidity and Mortality Weekly Report (MMWR).
Crunching the data
In beginning of the pandemic in March 2020 saw various US states and territories implementing various community mitigation policies – stay-at-home orders being the most widely implemented strategy at that time. Since each state or territory in the United States has the authority to enact its own laws and policies to protect the public’s health, and jurisdictions varied widely in the type and timing of orders issued related to stay-at-home requirements. With an intention to identify the broader impact of these stay-at-home orders, the researchers analyzed changes in population movement relative to stay-at-home orders issued during March 1–May 31, 2020, by all 50 states, the District of Columbia, and five US territories.
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During this period, 73% of the counties (in 42 states and territories) issued mandatory stay-at-home orders. The study finds a decrease in median population movement among 97.6% of counties for which data was available. Population movement significantly increased — i.e., lower median percentage of devices at home — in the period immediately after the expiration or lifting of orders in all rural-urban strata.
The analysis used four types of order index dates, based only on mandatory orders: the start date of each state or territorial stay-at-home order for each county in that jurisdiction; the relaxation or expiration date of each state or territorial stay-at-home order for each county in that jurisdiction; the effective date of the first state-issued stay-at-home order (i.e., California); and 4) the first date a state-issued stay-at-home order ended (i.e., Alaska).
