I've seen that some people never even show symptoms. They're tested because they were in contact with someone who DID show symptoms, like the people coming off the cruise ships. To start with they were trying to identify the cases as if it was something as deadly as ebola. So even the 1/2 of 1% is undoubtedly overstating the case of lethality. Including the people who don't ever show symptoms into the denominator will bring the mortality down below the 1 in 200 rate. How far down we don't know. 1 in 500? 1 in 1,000? 1 in 10,000? Who knows? If you isolate not only the aged, but also those who are health-compromised, you'd probably cover almost all of those who might die from the disease.
There are more and more symptomatic people being found through testing. Granted most are mild cases. Should we shut down the economy for a while? Not sure. The isolation greatly limit the spread and keeps it away from the old and infirm. I'm pretty sure shutting down for a short time is useful.
So even the 1/2 of 1% is undoubtedly overstating the case of lethality.
True, but flu is 1/50th of 1% in the same category of people. Even with the undercount of cases this is clearly more lethal.