[odkamkfn]

The testing rate is low almost everywhere. The mass testing done in the Italian town Vò suggests that 50-75% of infections are asymptomatic (but still contagious). This matches the findings from the cruise ship "Diamond Princess".

Also note that the populations of both the cruise ship and Vò skew quite a bit older than the world average, and younger people are more likely to be asymptomatic (AFAIK we still don't know how more likely)