Chat about Novel Coronavirus - 2019-nCoV - COVID-19

Ta, from the transcript:-

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The second question I often get asked is, why aren't we adjusting for countries' population sizes in this chart? So this one is a bit more of a judgement call. What we have with this virus is something which spreads at a fairly consistent rate regardless of the situation on the ground. We tend to see over a certain number of days the same number of cases, after day one, day two, day ten, et cetera.

And that's because this virus, it does spread fast, but it doesn't, you know, ripple through a country's entire population in a matter of days. So the overall population of a country is not any sort of limiting factor on how fast it spreads. It will tend to spread as the people in those cities, in those areas mix at similar rates at the same rate.

Now, we could, of course, still adjust for population, and give you sort of per capita or per million people numbers of cases or deaths. What that would do is essentially just make larger countries look like their outbreaks aren't quite as bad, and smaller countries look like theirs are much worse. With this chart, we're focusing on trajectory. We're focusing on saying, where are things right now, where are they going to be in a few days, and how does this compare to other countries that you're already familiar with from following the news.

So if we changed to per capita, the slopes wouldn't actually change. All that would change is the vertical positioning of different countries' lines. And they would change in such a way that, for example, the American outbreak would look less alarming than it is, and the Danish or Swiss outbreaks would look worse. The numbers that come up in the news, and the numbers that we as humans instinctively react to are numbers of people, numbers of deaths.

I think if we start moving into per capita, per million people rates, first of all, you lose a bit of the immediacy, a bit of the sort of visceral nature of these numbers. We would lose that connection with the numbers that we're seeing in the news. We're hearing about hundreds and thousands of people being infected and dying tragically in countries like Italy and Spain. And I want people to be able to see on that y-axis where they are in relation to that, not where they are in relation to some more abstract number, which loses, as I say, some of the sort of emotional power that I hope this chart has.
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