They used location data from more than 45 million cellphones between March 11 and April 10 to work out daily travel distance and time spent at home across all 50 states. This helped them judge how well people obeyed social distancing mandates.
It looks like they did, to some degree.
“Implementation of stay-at-home social distancing policies were associated with human movement changes,” the researchers wrote. “That is, people generally reduced their daily travel distances and increased their home dwell time.”
At the same time, the rate of increase in cases in the five states with the highest level of infection at the time — New York, New Jersey, Michigan, California and Massachusetts — slowed down after the stay-at-home orders were implemented.
Their results “suggest that stay-at-home orders were associated with reduction of the Covid-19 pandemic spread and with flattening the curve.”
It’s possible other control measures — such as mask wearing — could have played a part in the reduction of cases.
Once orders lifted, movement increased
“Based on location data from mobile devices, in 97.6% of counties with mandatory stay-at-home orders issued by states or territories, these orders were associated with decreased median population movement after the order start date,” researchers from the CDC and the Georgia Tech Research Institute wrote.
The researchers also found that in areas where orders were lifted or expired, movement “significantly increased” immediately afterward.
The studies can help governments decide how to control the pandemic in the future, the Wisconsin researchers said.
“The findings come at a particularly critical period, when US states are beginning to reopen their economies but COVID-19 cases are surging,” they wrote.
“At such a time, our study suggests the efficacy of stay-at-home social distancing measures and could inform future public health policy making.”