One possible way for this to kinda sorta work is that perhaps there are people who get tested in order to show a negative test, whose tests get reported every time, and people who get tested because they want to actually know if they have Covid, who mostly only report when they’re positive. Then, doubling the size of the second group doesn’t change reported test counts much? That’s the best I can come up with.
My mental model (backed by nothing) is that a lot of people get tested due to symptoms that often aren’t due to covid, so this provides a relatively constant level of negative tests even though they do actually want to know if they have Covid. (In addition to any who simply want a negative test, of course).
It’s possible that perceived prevalence would affect the tendency to get tested for a given level of symptoms, but if so I wouldn’t be surprised if this perceived prevalence lags the positive tests. (There’s a lot of potential for weirdness here though).
People getting tested due to an interaction with a positive case would provide negative tests correlated with positive tests, but I expect this would lag the positive tests.
Just speculating—I haven’t been paying attention to the negative test patterns in the past, so this might for all I know be totally at odds with the actual data.
My mental model (backed by nothing) is that a lot of people get tested due to symptoms that often aren’t due to covid, so this provides a relatively constant level of negative tests even though they do actually want to know if they have Covid. (In addition to any who simply want a negative test, of course).
It’s possible that perceived prevalence would affect the tendency to get tested for a given level of symptoms, but if so I wouldn’t be surprised if this perceived prevalence lags the positive tests. (There’s a lot of potential for weirdness here though).
People getting tested due to an interaction with a positive case would provide negative tests correlated with positive tests, but I expect this would lag the positive tests.
Just speculating—I haven’t been paying attention to the negative test patterns in the past, so this might for all I know be totally at odds with the actual data.
Also, people who get tested because they need to show proof of a negative test for some purpose would be part of this background rate as well.
Yes, as Zvi mentioned in the quote and I acknowledged.