Google is revealing anonymized location data on the movements of people in 131 countries as a guide for public health officials during the coronavirus pandemic.

The reports, available in PDF format, show how visits to broad categories of places–such as retail and leisure establishment, grocery and pharmacy stores, and residential areas–have changed in the past two months. The data show median daily visits to those categories for the three days ending March 29, compared with the median number of visits between January 3 and February 6.

pAn excerpt from Google's report showing the change in visits to categories of places in California between late March...
An excerpt from Google’s report, showing the change in visits to categories of places in California between late March and January.
Courtesy of Google

The numbers are not surprising, given the widespread shelter-in-place orders that generally bar people from leaving their homes except for essential trips like grocery shopping. In San Francisco, where a shelter order has been in effect since March 17, visits to retail and recreation sites fell 75 percent compared with earlier in the year, while visits to what Google classifies as residential areas increased 21 percent.

The idea is to help public health officials around the world evaluate how well social distancing measures are working and identify places where new policies might be needed. For example, if too many people are gathering at public transit stations, it may be a sign that more frequent bus or train service might be needed.

“This is exactly the kind of information we need to understand the impact of our mitigation measures on movement and to inform our decisionmaking,” Santa Clara County, California, public health director Sara Cody said in a statement.

Google gathered the underlying data from users who have the “Location History” setting enabled in their Google accounts. Google draws on the same date in Google Maps to display how busy particular restaurants and other locations are at a given time. The company says the setting–which it says “Saves where you go with your devices, even when you aren’t using a specific Google service”–is off by default, though some apps prompt users to turn it on.

pAn excerpt from the report for San Francisco.p
An excerpt from the report for San Francisco.
Courtesy of Google