There’s a very useful statistic that I have not seen from any government source in the U.S.: the percentage of asymptomatic hospital patients who test positive for COVID-19. That is, if someone enters the hospital system for something other than COVID-19, what is the chance they have COVID-19?
It’s not a perfect statistic. It could be biased towards people who are more likely to take risks regarding COVID-19–someone who twists their ankle ordinarily might go to the emergency room, but maybe now some people decide to wait it out a bit (or go to a doctor’s office first). It also would be biased towards women ages 20-35 (that baby is coming whether you want it to or not) as well as elderly people (heart attacks, etc.). Still, it would give us a rough estimate of the actual prevalence, and changes over time, to a considerable extent (there might be seasonable variation too), would tell us how things are changing. I think it would be very useful, though like other statistics, it shouldn’t be interpreted in isolation.
Other than the University of California hospital system, I haven’t seen any release of these data. It’s something that should be done nationally.