Google recently released the results of an analysis of mobility data. These results are very interesting, especially when cross regional comparisons are made. In brief, these results tell us how much society is using public spaces–like grocery stores, retail outlets and parks–and is an indirect indicator of physical distancing behaviour. Below are a few of my early observations.
Where do we go now?
Regions that have been identified as locations of high levels of infection and mortality appear to have the greatest reduction in visits to retail outlets, workplaces and other public destinations in our communities. Here is a figure for Italy:
What we see is a 94% reduction in Italian visits to retail and recreation locations as of March 29, 2020 compared to a baseline of activity from a few weeks prior. The decline started in early March, when news of Italy’s health care crisis was first emerging.
In contrast, here is a figure for Sweden:
Note that the drop is much less dramatic, and the decline starts around March 8th. It’s worth noting that Sweden has a different take on the covid-19 crisis. There is little mandated physical distancing. Most public health policy is focussed on vulnerable populations and prohibition of large gatherings.
In Canada, it looks like this:
Canada saw a later start to the decline than Italy and Sweden, but has seen a dramatic reduction nonetheless. The US data as a whole look very much like Canada’s, though the magnitude of reduction is a bit lower (a 47% decline from baseline as of March 29th). However, this varies from state to state. In New York, for example:
In Arkansas, on the other hand, the reduction has been less dramatic:
Also interesting is the change in activity by location type. National parks, public beaches, dog parks and public gardens have seen less of a decline in activity over time. In Canada, we see a smaller drop in the use of these park spaces:
Perhaps this makes sense–people need to get out for exercise, and view these spaces as safe (given their spaciousness, and our feelings towards to the healthiness of nature generally). Moreover, in much of Canada, we are coming out of winter, and many people are clamouring for sun.
In Australia, where climate is warmer generally, and seasons are reversed from those in the northern hemisphere, we see a larger decline in use of parks over this period:
What does this all look like in countries where novel coronavirus has been around for a while? Well, here are some figures for South Korea:
We can see here that South Korea did not seem to rely as much on physical distancing for infection control, at least not to the same extent as many countries are doing now. Note that visits to parks and grocery/pharmacy are actually up. I should mention that these comparisons are a little tricky, as we don’t know what happened in early February or January, and I am unsure what Google uses as a baseline for South Korea; if it’s the same for everywhere around the world, it’s hard to know how to interpret the data for countries that experienced the outbreak earlier.
There are no data for mainland China, but there are data for Hong Kong and Taiwan. Here are some figures for Hong Kong:
Based on these data, residents of Hong Kong seem to be pretty consistent in their mobility behaviour for at least the last 6 weeks or so.
What does this all mean?
At this point, it’s very hard to say much about these data beyond what we see from these figures. I wish Google would put this in a table with day-specific records; as it stands, all we can do is look at the graphs, and can’t really analyze many numbers yet. Still, I think these data could be useful in the next few weeks, when we can compare the trends in mobility to trends in cases, testing and deaths (notwithstanding the very low quality of infection data right now). At some point, we could see some connection to mobility behaviour and testing.
However, one observation that could be important here is that the most extreme physical distancing behaviour is a response to crises already in force. New York state and Italy and other areas with a large number of cases and/or deaths take this practice most seriously, but only did this once the the infection was well under way. In other areas, physical distancing has been employed less, but (at least in the case of South Korea…maybe), the infection still flattened with less radical levels of physical distancing behaviour. Maybe something else that Koreans were doing (like wearing masks…?) is what really accounted for the decline in infection. This is all still pretty speculative now, but the data (so far) do not seem inconsistent with that hypothesis.