So early on I was suspicious of the numbers from China, but since they have managed to control the spread (and it would be obvious if they didn’t and other cities started to look like Wuhan), that means they have done a good job of catching almost all of the cases, not just the symptomatic ones. Otherwise the ones they miss would continue to spread.

Therefore it feels like at this point their data would be pretty representative of what percentage of the cases are severe vs critical and what the death rate is (accounting for both the overwhelmed medical case in Wuhan and for the under control case in rest of China).

South Korea is also doing a pretty good job with testing to control the outbreak although they haven’t yet gotten it as under control as China does. So their numbers would be a good data point to cross-validate the China numbers.

In countries like Italy (or Wuhan early on) the number of confirmed cases wasn’t equal to total cases as evidenced by continued growth of the epidemic. So it’s reasonable in those cases to assume that more severe cases are being found and less severe ones are being missed.