"the NYC antibody study one you mention, done at shopping centers, indeed likely over-represents people going out." The samples were done at grocery stores. No

"the NYC antibody study one you mention, done at shopping centers, indeed likely over-represents people going out." The samples were done at grocery stores. Non-essential businesses are closed in New York. Most people here still have to go out to get groceries. There is no evidence that this has led to an oversample; these are hypotheses advanced by people on reddit and HN.