slats11 - great post.
I think the South Korea data is probably the best for looking at CFR (circa 1%) - they have done the greatest level of testing as far as I can see and also have one of the lowest CFRs. So either a) they have a best treatment/health service response, or b) they have weaker "strain" of Covid (2 have been identified but no one seems to think one is more or less virulent than the other) or c) they have a much better (and higher) count of overall cases as they have been testing the most people?
This sort of assumption also works for the current UK CFR numbers that to me look high as a proportion of overall cases but we've only been testing folks who have presented at hospitals with significant symptoms.
There's no way to prove any of this is true/false at the moment as we don't have apples or oranges to compare. That being said your analysis looks sensible to me.
We would all like Korea's CFR. It is low because
1. A lot of cases were in the religious cult = young adults
2. They rounded up and tested the members of that cult - and diagnosed cases where people were positive but had no symptoms (= very mild disease). It is hard to die from a resp infection if it is not causing any resp symptoms. All these subclinical cases got bundled up into their CFR. In Australia, these people are walking around spreading the disease.
3. Unlike UK, Italy, USA, Aust etc, Korea has increased its number of beds over time in line with its ageing population. Oddly enough, we have done the opposite. So they have a greater surge capacity.
China did a neat trick for 48 hours. Allowed clinical and radiological diagnosis (rather than microbiological confirmed) for 48 hours to get a whole lot extra cases (15,000 from memory) into their dataset - and significantly lower their CFR.
