The point is that if the disease spreads so quickly, and our best evidence from months ago is that 20% of the city was infected, it stands to reason that much m

The point is that if the disease spreads so quickly, and our best evidence from months ago is that 20% of the city was infected, it stands to reason that much more of the city was infected than 20%. How much more is up for debate. A competent government would be regularly conducting these surveys and publishing the results. We have been more open, with many protests, streets full of open air bars, etc. for months. I would bet $100 that NYC, if we could do a full antibody and t-cell assay, would show the majority of the population was infected. Furthermore, I would submit that R0 as a crude instrument ignores network effects. I'd wager anyone who is a "super spreader" in NYC has been infected at this point. Some papers have suggested a 20% herd immunity threshold taking into account the network effects. I doubt it's that low, but it is an important factor to consider.