Isn't it consistent though? There is a confidence interval associated with all of these numbers and the intervals are quite wide.

What if there are other, undiscovered factors that could explain the difference? Such as NYC populace having had exposure to some other virus that predisposed them to a greater vulnerability. Or perhaps, air pollution exposure predisposing them to greater vulnerability.

We have two possible hypotheses.

There is an unknown quality about New York that causes the virus to be 4 times more severe.

A self-selected group from the internet demonstrated self-selection sampling bias.

I know where I would put my money.

I think there's significant error bars all around. Note that the New York data is older than the SCC data, so there's delay related effects, too.

We can quibble a whole lot with exact effect magnitudes and data analysis techniques, but...

In any case, we have a whole lot of data (Iceland RTPCR, Gangelt RTPCR, Switzerland RTPCR, Netherlands blood donation serology, Santa Clara County serology) that indicates infection rates likely exceed case rates by 10x or more in areas with relatively good testing availability.

Take 30 times 0.15 you get 4.5. I wouldn't draw any conclusions due to the low quality of current data.

Just a hypothesis, but if being more frequently exposed makes it more likely that the disease will be more severe, then this is plausible. There is some evidence that e.g. doctors/nurses were more likely to die compared to their age cohort, possibly because of higher viral load.

I've definitely seen the opposite stated, that doctors/nurses are not actually more likely to die. I forget if it was Italy or NYC, but the fatality rate for doctors & nurses had been something like 0.5%. They are much more likely to be infected than anyone else, and there has (rightly) been lots written about the doctors and nurses who have died, which gives people this perception.

I don't think virologists thing frequency of exposure is very important to lethality. But there is evidence that dosage and stress play a roll which will both be higher in medical personnel.