When comparing the raw number of coronavirus cases you may wonder how the population of a country plays into it.
Here we compare confirmed coronavirus cases with confirmed coronavirus cases adjusted to the population of each country. The numbers used here are from the Johns Hopkins Coronavirus Resource Center’s GitHub database.
Each figure we’ll look at compares the top 10 countries with the most confirmed coronavirus cases to date.
The plot begins when each country hits 1 confirmed coronavirus case per million residents. As you can see the United States is on day 15 since the first case per million residents.
The population-adjusted numbers show the spread of the virus as a function of population size. While China falls the lowest in the plot when adjusted for its population you’ll see below it is the highest in total number of cases.
The rapid increase in cases/million residents for the United States specifically is partly due to an increase in recent testing, which has “caught us up” to more realistic case numbers.
Zooming out to 30 days from reaching 1 confirmed case per million residents you can see China was able to continue to flatten the growth, as was South Korea.
Italy stands out, which is still seeing exponential growth, as does Switzerland, Spain, the United States, and Germany.
While these plots may make it appear that the United States is middle of the pack in terms of coronavirus case growth, looking at raw coronavirus cases paints a very different picture.
Here is the same plot as the 1st plot just without correcting for population size. You can see that this paints a very different picture with the United States at the 2nd highest number of cases at this point in its curve.
Zooming out to 30 days you can see that the United States is growing quickly early on in its curve, far more so than any other country in the world except China.
The big question is which figure is a more realistic representation of today’s picture of each country?
John Burn-Murdoch, a data/stats journalist who has become popular for his visualizations of coronaviruses through time, argues that while adjusting for population may show the relative strain on a country, the growth of the virus should be independent of the size of the country.
The more important factor here would be population density in an area where there are a significant number of coronavirus cases. Places like New York City, London, etc. where we’re seeing extremely rapid growth.
If you have a scenario where there are 10,000 coronavirus cases in a country with 300 million residents and one with 30 million residents, the virus will grow the same all other factors being equal. Virus growth is relatively independent of the total population size (see Daniel Bernoulli’s epidemiological model revisited).
Thus, the raw numbers of cases are more telling on the current situation of a country. Population density, quarantining, human behavior, etc. playing a much larger role in how the virus spreads than the total population of the country.