Honestly, I have no idea. You’re absolutely correct - we need a uniform standardized set of data to make comparisons. As to not wanting be tested, the numbers are obviously skewed because the only people that are tested are those who think they NEED to be tested. I’ve never been tested and don’t particularly care to have a 6” Q-Tip shoved into my forehead either.
Mexican positivity data is especially skewed. Pretty much useless.
I think people are probably similar all over. Who wants to be tested if they feel they are not at risk or haven't been exposed. But aside from the deep swabbing up the nose (why can't you just cough on a test strip if it's so contagious?) there is the privacy issue. No one wants to go into a central database and forever be marked not knowing how it may be used against you later?