Is social distancing working?
Using Apple’s mobility tracking data to measure the effectiveness of social distance in controlling Covid19
Apple released a mobility data trends (www.apple.com/covid19/mobility) that uses data from Apple Maps to show how people’s driving, walking, or taking public transit behaviors changed over time. This data can be used as a proxy to measure how people’s movements have decreased or social distancing has increased. Peoples’ movements in major cities, regions, or countries are tracked and reported as normalized numbers since Jan 13, 2020. Combining this data with daily number of reported Covid19 cases (https://covidtracking.com) can help examine the relationship between social distancing and controlling the virus.
There are a total of 14 U.S. cities being tracked (Los Angeles, SF-Bay Area, Denver, Miami, Atlanta, Chicago, Boston, Baltimore, Detroit, New York City, Philadelphia, Dallas, Houston, Seattle). The mobility trends of these cities are combined with the daily counts of Covid19 positive cases to create plots below.
The dotted vertical line is the date of stay-at-home order was first issued. In San Francisco-Bay area, people’s movements started to slow down well before the statewide stay-at-home order date (3/19/20). Similar behaviors can be seen in other cities, including states issued a stay-at-home order in April. As states ramping up more testing, the number of confirmed cases has been rising even with social distance orders in place.
While some states swiftly issued the stay-at-home order, some states were slow to react. So, the timing of the order can be a good variable to split the data into control/test groups to check any variabilities among two groups can be seen.
In Group1, the following four states are chosen — CA (3/19), IL (3/23), MA (3/24/), MI (3/24). NY is not chosen as it can skew the overall data. In Group2, states that issued a stay-at-home order starting in April are chosen — FL (4/3), GA (4/3), PA (4/1), TX (4/2).
While driving behaviors are similar in two groups, noticeable differences can be observed in walking and transit. Regarding transit behaviors, both groups show significant drops since Jan-13. However, the states in Group1 show a steeper decline (-80% in April) in requesting transit routing than Group2.
Each state has different testing capabilities and administrates. In order to limit the impact of few states skewing the daily increase in Covid19 counts, daily % increases are compared. In the beginning of March, both groups show large spikes. However, while Group1 states were able to control the daily % increases later in March, Group2 states continued to show large spikes throughout March. Interesting to note that once Group2 states had stay-at-home orders in place starting in April, daily% increase in Covid19 started to come down to a more manageable level.
Like everyone says, social distancing is important combating Covid19. Hope this provided some insights.
