I think that 20% is way too high and the number is skewed due to a lack of testing kits in many countries.
Just take Germany as an example, they've been testing people extensively, over 9k confirmed cases and 26 deaths so far with 2 other patients being in serious critical condition right now.
Let's do the maths here: 26 (deaths) / 9,367 (confirmed cases) * 100 = 0.28% death rate.
Way lower than the world average at around 4% (deaths/total infections).
Also Norway for example: 3 (deaths) / 1,468 (confirmed cases) * 100 = = 0.20% death rate.
They currently have 27 patients in serious/critical conditions in Norway: 27 (serious/critical condition) / 1468 (confirmed cases) * 100 = 1.84%
Not even close to the 20% you proposed.