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In the early days of the pandemic — March into May — testing was scarce, limited mainly to victims, first responders, and essential workers in pandemic “hot spot” areas such as New York City, so you would expect the percentage of confirmed cases to be high.

But by mid-May, testing in the general population was extensive as the “hot spots” in the northwestern and northeastern regions of the U.S. subsided, and “hot spots” popped up in the southern and southwestern states. So, assuming that testing is now essentially random among the population, the 8% rate appears to me to be a “baseline” nationwide infection rate, at least until any remaining “hot spots” disappear and the pandemic ends.

If extensive random testing had been available back in March and April, we would expect the true nationwide infection rate to have been around 8%, because that’s what we’re now seeing with massive testing and the current “hot spots.”

Applying the 8% baseline infection rate to the entire population, this means that every week after the beginning of April, another 2.67% of the people in the U.S. had recovered from COVID-19, were immune and non-contagious, and were not a threat to anybody. These numbers are additive. By July 17 (15 weeks), 40% of the country is now immune to the coronavirus, whether or not these people know it, and they cannot infect anybody else (for as long as the period of immunity lasts, likely well into the fall).