Not really. Antibody tests like this one measure the total number of people who've been infected at some point in the relatively recent past, whereas the diagnostic tests New York is using only detect current active infections, so it's easy for the percentage of infections measured by the former to be higher than the latter.
When articles like this compare the number of known cases detected with the PCR diagnostic tests with the higher estimate based on antibody testing, they're comparing the sum of all cases detected since the start of PCR coronavirus testing with a point-in-time estimate of the proportion of the population that currently has antibodies for exactly this reason.
That’s true. We could have 25% active infections and 25% not currently infected but who were infected in the past. I still think the actual numbers may be be lower (but higher than the reported figures, of course).
My point was that the number of people currenlty infected is surely lower than 30%, given that only 2% of the population is already confirmed and testing a suspected case today will return a negative 70% of the time.
But as another commenter said, it's not impossible that there are many other people who had infection which is not currently active.
Using the overall test rate doesn't really help, I think.
It doesn't seem that unlikely to me (I live here). I know so many people, me included, who had it but aren't included in any official count for lack of testing, and so many others who must have had it (e.g. my cohabiting SO) who were asymptomatic.
