Honest question: if there is really an increase in cases across the US, shouldn't we see an increase in positive test result rates (# confirmed / # tested)?
The positive test result rate continues to decrease across the United States, albeit more slowly as of late.
(1) It's important to make sure the numbers you're using are directly comparable -- e.g., if #confirmed is the count of unique individuals who are confirmed to have the virus and #tested is the number of tests administered rather than the number of people who have been tested then you won't get the expected results.
(2) There can be confounding variables like choosing to test people with milder symptoms.
(3) False positive/negative rates can be a factor (though they shouldn't be in a halfway decent test). If your false negative rate is x and your false positive rate is greater than 1-x then your positive test result rate will fall as your true positive rate rises.
(4) Etc. The problem is that the numbers you're measuring (reported test results) aren't the numbers you care about (true infection rates). They might align, and they will mostly align with good tests and unbiased data that are correctly and honestly reported, but they don't have to.
Caveat: I haven't been closely following covid news and have no idea how much any of those potential discrepancies might apply IRL.
The significance of positive test rate rates is extremely dependent upon the slectiveness & availability of testing, which has trended higher but has varied in extreme ways.
Initially, only the sickest patients, most obviously suffering from COVID-19, were eligible for testing. We would of course expect positive test rates to be sky-high during this time, as we were only testing those whom we were pretty certain were infected and were suffering life-threatening symptoms.
Now, tests are more widely available. Testing is no longer tightly constrained to the most obvious suspected cases. So, with a wider swatch of the population being eligible for testing, we would probably expect the % of positive test rates to fall even as the number of infected goes up.
Looking at only the US numbers hides some of the picture. For example, there's this chart from about a month ago showing that only looking at US numbers without breaking them down can be misleading: https://www.axios.com/us-coronavirus-new-cases-second-wave-n...
The positive test result rate continues to decrease across the United States, albeit more slowly as of late.
I really do mean this as an honest question.