Please be careful with every study you read or be talked about in the news: there's over one thousand studies on Covid19 so far, with a big discrepancy in results. Cherry-picking the one we want to hear is pretty dangerous if it gives us a false sense of security.

For the record, on the Diamond Princess (with everybody tested) the number of asymptomatic case was 60% with more than 1% death rate with Japanese healthcare (not overloaded). You can't generalize on these figures either for many reasons but thats's still a strong warning.