Here is the summary of a report on antibody testing that just came out of Santa Clara County, California. Basically, the number of people who had antibodies was 50-85 times higher than the number of reported cases in the county. Based on a sample of 3,330 people.
I thought the actual number of cases was probably 10-15 times higher than what's been confirmed. 50-85 times higher is significant.
That would be either bad news, or good news. Bad because it means we have under tested by way more than most people would have predicted, and the virus has infected way more people that previously though. Good, because it means the mortality rate is significantly lower than what has been "confirmed" so far, and the fact that a lot of people already have antibodies will help slow the spread. If 15% of the population are immune, it doesn't stop the virus, but it does slow the infection rate significantly.
Studies in other countries have produces similar results. We should be watching closely as more of these studies come out throughout the U.S.
https://www.medrxiv.org/content/10.1101/2020.04.14.20062463v1