Here's a chart made from a study in China. It's actually a bit unclear, but I'm assuming it's 18.5% of confirmed cases that require hospitalization. Now, the question is how many of those that got sick at all got confirmed in China, and how many people presented symptoms (those are unknown).

So it seems like it's less than 18.5%. On top of this, Chinese men are heavy smokers and the air quality in China is pretty terrible, so that may play a part as well.