Is it wrong, though? I did read the article, and I don't think so. One relevant thing GP may have missed is that the researchers "excluded anyone who had teste

Is it wrong, though? I did read the article, and I don't think so. One relevant thing GP may have missed is that the researchers "excluded anyone who had tested positive for the virus in the standard nasal swab test". So they weren't quite trying to directly estimate the proportion of people with antibodies, but the proportion of people without a positive test with antibodies. But I suspect this didn't change the results much: how many people in the area have tested positive and recovered sufficiently to be out in public?