US mortality rate not what it seems
The US may have over a million cases of coronavirus, a third of the world's total, and 70,000 of its citizens may have died - but by some measures it's actually coping with COVID-19 rather well.
That's what President Donald Trump and a number of his health advisers would like you to know.
Not that he hasn't expressed his sorrow at the sheer number of deaths. Yesterday, he told Fox News that 75,000 to 100,000 Americans could die.
"That's a horrible thing. We shouldn't lose one person over this."
But he and his administration have also been pointing to another stat.
"Our death totals, our numbers per million people, are really very, very strong. We're very proud of the job we've done," he said on 1 May.
For some time, Dr Deborah Brix, the country's senior medical adviser, has also been pointing to deaths per million.
"Our mortality is significantly less than many of the other countries when you correct them for our population," she said in April.
Death per capita or per million figures are several of the multitude of COVID-19 stats that have become common currency. Depending on which you choose can make one country look like it's looking poorly, or not that bad after all.
But which measures are actually useful in showing how well one country is doing against another? Total numbers, growth, cases/deaths per capita or cases/deaths compared to tests?
"There are no perfect measures. Comparing countries is very tricky because they often measure deaths differently," RMIT computer scientist Professor Mark Sanderson told news.com.au.
"Belgium has a huge death rate, but what they count as a coronavirus death differs to other countries. The UK changed the way it was counting deaths last week (by including deaths in nursing homes for the first time) so it makes comparing very, very difficult."
WHAT TINY SAN MARINO CAN TELL US
Looking at deaths per million people, the US does indeed look better than some countries.
The US has around 200 deaths per million people. By this metric, a host of European nations have fared worse; already mentioned Belgium has 676 deaths per million, Spain 540, the UK 419.
However, suggesting the US' mortality rate is "significantly less" than other "many" other countries is a furphy. Most countries are in fact doing significantly better on that measure.
Germany has had 80 deaths per million, and China and Australia only about 3 per million.
There are fundamental issues with relying on the metric of per population figures during a pandemic. That's illustrated by the worst affected country by this measure: San Marino.
You can be forgiven for not knowing much about San Marino. It's a tiny country, high in the mountains completely surrounded by Italy.
However it has an astonishing 1208 deaths per million people or 121 deaths for every 100,000 residents. That's if it had 100,000 residents; it actually has 33,000.
IS IT A FAIR MEASURE?
"Very small nations typically creep up those sorts of measures just due to an incident; a few more deaths in a very small nation can cause that country to go further up the rankings," said Prof Sanderson.
A pandemic might rip through exactly the same number of people in two different countries but in the small nation it could look far worse particularly if in the larger country the virus has only affected a few areas so far. Also a country that is later in the pandemic, like San Marino, may look like it is faring worse than one which is earlier in the outbreak.
If coronavirus were to affect other parts of the US as it has New York, deaths per million would rise. Indeed, last month the US was at 50 deaths per million people, now it's quadrupled that.
In total, San Marino has had 582 cases and 41 deaths which puts its case to fatality rate at 7 per cent. That's not great but it's also far better than the UK, Spain or even neighbouring Italy. That rate is more than the US but less than the 8 per cent fatality rate in New York City, the epicentre of the US epidemic.
That's why some statisticians prefer to look at individual affected regions - like New York to Lombardy - as they are more easily comparable and numbers don't skew as much if one is in a larger country.
Australia's case to fatality ratio is 1.4 per cent, which is low. We have 0.38 deaths per 100,000 people - the US is on 20.69 deaths per 100,000 and Belgium 67.
'TRAGICALLY USEFUL' STAT
Many experts prefer to focus on logarithmic graphs that show how fast cases are increasing in each country compared to one another.
Looking at this measure, the US has had the most sustained rise in infections as well as the largest overall.
By this chart, Ecuador looks to be the nation that has most failed to "flatten the curve" - it's actually sending it skyward again with an upswing in deaths. Although it's also shot up in testing people for COVID-19 too.
A crucial number is the number of tests being conducted and the amount of positive cases per tests.
"If only a fraction of tests comes back positive that certainly suggest there's not many cases," Prof Sanderson said.
Again, this measure puts Australia in a good light. On average we've had to test around 100 people to find just one case. But in the UK and the US, authorities are having to do just five to six tests to get a confirmed COVID-19 diagnosis.
In terms of tests per 1000 people the US is doing better. It is below Australia, New Zealand and Italy but above the UK.
As Prof Sanderson said, there are no perfect measures to comparing different countries.
Take Italy and Spain's high number of deaths. Sure, there are questions about how prepared their health systems were, but they also have elderly populations who were always going to be more susceptible.
"Excess deaths is a measure I find it tragically useful. If you look at the UK you might read about several thousand people dying in a week but you don't know if that's a lot or a little," he said.
"But when you see that number is double what you'd expect for that week, you suddenly realise this is a big deal."
By most measures, the US has not coped with the coronavirus crisis well. Neither has the UK, France, Italy or Spain.
If the US can control the world's worst outbreak and keep deaths from rising much beyond where they are now, then the deaths per million figure could be useful eventually. It could show, when the pandemic is over, if it managed to contain the virus.
But that number's usefulness right now is questionable, aside from making the US look not quite as worse as other countries.
Originally published as US mortality rate not what it seems