Personally I'm still watching the Diamond Princess situation to get an estimation of overall mortality rate... that's a contained situation plus it's been ongoing for 2 months now and there are still several serious/critical cases.
11 deaths from 712 cases... ~1.5% which is likely the best estimate we can get for how deadly the virus is in a wider worldwide population.
In countries with a higher death rate than ~1.5%, there is likely to be MANY more cases which would pull that death rate closer to ~1.5%... and in other countries where the death rate is less that ~1.5%, I'd suspect that either some deaths weren't/aren't being counted as Covid-19 deaths and/or the death rate is still on the rise as critical/ICU cases could still lead to more deaths and a rise in the actual mortality rates in those nations.
Coronavirus Update (Live): 1,118,202 Cases and 59,220 Deaths from COVID-19 Virus Outbreak - Worldometer
According to the stats there's been a reported 1,118,059 cases worldwide and 59,206 deaths... which gives a mortality rate of ~5.3%
If we assume ~1.5% is the "real" mortality rate then we can assume the REAL case count is likely much higher as well.
5.3/1.5 = 3.53
From those stats above we can roughly estimate that there are probably ~3.53 times as many cases as have actually been reported... (many mild and uncounted cases across the world because of lack of systematic testing).
If that's the case the "truer" estimate for the number of cases across the globe is likely ~3.95 million instead of the 1.12 million currently reported.
If that's true (and of course that's all calculated on the basis of some assumptions and rough estimates as well)... the good news is that the mortality rate is lower overall than we think it is currently... but also the bad news is the rate of proliferation of the virus is likely MUCH higher as well than we think it is currently.
(I also realize that it's still a rough overall estimate as different countries have slightly different and sometimes very different average/median ages for their populations which could/would affect the results above as well.)