Population Density and COVID-19

The first two days of the week have looked great for Tennessee. Tuesday the 5th was a particularly good day. There were 146 more recoveries than new infections reported. Getting more days like this is key to not only flattening the curve, but crushing it. Although some states like Tennessee seem to be doing pretty well, others, like Illinois, are reporting 2,000 new cases each day.

I did some state level analysis today to look at the effect of population density and temperature on the number of deaths per million people. Temperature has no correlation with number of deaths normalized for state population. This is unfortunate, since it could mean there is little or no seasonal effect. However, population density is highly correlated with the number of deaths in a state normalized for population. It explains one-third of the variation in the number of deaths per million people in a state. See the graph below.

Alaska, with just 12 deaths per million people, is on the left end of the graph. Northeastern states like New York, Connecticut, Rhode Island, and Massachusetts are at the right end. The data do not account for differences in population density across the state. Virginia, for example, is densely populated near D.C., more so than Nashville or Memphis. This may explain why Virginia has 80 deaths per million people, while Tennessee has only 32. This is a factor of 2.5, even though the statewide population density of Virginia is only 60% greater than Tennessee’s.