Coronavirus: Why are international comparisons difficult?
- But there are all sorts of challenges in comparing countries, such as how widely they test for Covid-19 and whether they count deaths from the virus in the same way. Prof Sir David Spiegelhalter from Cambridge University has said trying to rank different countries to decide which is the worst in Europe is a "completely fatuous exercise". -
- First of all, there are differences in how countries record Covid-19 deaths. France and Germany, for example, have been including deaths in care homes in the headline numbers they produce every day. But the daily figures for England referred only to deaths in hospitals until 29 April, when they started factoring in deaths in care homes as well. A further complication is that there is no accepted international standard for how you measure deaths, or their causes. -
- There is a lot of focus on death rates, but there are different ways of measuring them too. One is the ratio of deaths to confirmed cases - of all the people who test positive for coronavirus, how many go on to die? But different countries are testing in different ways. Early in the outbreak, the UK mainly tested people who were ill enough to be admitted to hospital. That can make the death rate appear much higher than in a country with a wider testing programme. -
- There are real differences in the populations in different countries. Demographics are particularly important - that's things like average age, or where people live. -
- not all testing data is the same - some countries record the number of people tested, while others record the total number of tests carried out (many people need to be tested more than once to get an accurate result). The timing of testing, and whether tests took place mostly in hospitals or in the community, also need to be taken into account. -
- So, is anything useful likely to emerge from all these comparisons? "What you want to know is why one country might be doing better than another, and what you can learn from that," says Prof Jason Oke from the University of Oxford. "And testing seems to be the most obvious example so far." But until this outbreak is over it won't be possible to know for sure which countries have dealt with the virus better. -