Why people keep saying that the coronavirus has a 2-3% mortality rate?

That rate has been calculated using the known cases. The problem with respiratory diseases is that there uses to be a high amount of mild or asymptomatic infections that go undetected. That means that 2-3% is a top limit. The real rate could be 10 times lower, or 20 times, or 100 times lower. It depends on the amount of mild and asymptomatic cases, and it seems to be quite high.

Just make a quick calculation. While the 2-3% rate is the average one, when it comes to people over 60, the calculated mortality rate was about 10-20%. In the Diamond Princess you had about 1000 cases, probably more, and most people there are over 60, 70 and even 80 years old.

If that 2-3% average mortality rate was the real one, you should have about 100 to 200 deaths in the Diamond Princess.Last time I checked, there were 6.