Many people are asymptomatic. A 5x number is likely low.
The only way to really know, would have been have worldwide, forced testing of every single person, weekly.
EG billions of test per week.
There were no tests at the start, not enough worldwide testing ability for the first 6 months, and once capacity existed, generally only people who felt sick were tested.
That's completely false. And don't "rich nations" this, as if your political view makes a point. We know that the asymptomatic rate for covid-19 is about 20% for adults, 40-50% for children, because we actually did massive testing of exposed people. Millions of tests were performed in the US, enough to get the positivity rate in most states down to 3-4%. There were not masses of 5x the positivity rate escaping these tests. And if you think everyone had it before the testing started, you're wrong, because the hospital records would have shown it.
You can't comprehend that richer nations would have better testing and would therefore have a better idea of how many cases they have...
And you think hospitals would have records of patients testing positive for a disease we had no knowledge of let alone means of testing before either of those came into place...
I quite well comprehend that richer nations have better testing. Those are the test results we have to go on (not Cameroon or North Korea - those would be blank guesses). The numbers are static across all nations that did serious population testing, so we actually do know the asymptomatic rates, and they are not 5x the diagnosed rates. They may well be 5x the positivity rate in poor countries that don't do much testing, but that still doesn't change the asymptomatic rate for people who have the virus.
Second point: Hospitals were recording symptoms of covid even prior to widely available testing, and as soon as the virus spiked their ICU beds were full. This has been the case in every country in the world. They didn't need to test patients. Those patients were dying in the hallway, and on ventilators. The spike was clear and obvious in each country when it arrived.
And in each country, the percentage of people testing positive who had no symptoms was roughly the same. So the argument that there have been 5x as many people as reported who had covid - and had no symptoms - is totally false.
Actual infections 5x the number of cases detected through testing in rich, developed countries with relatively widespread tests seems pretty plausible, I think there's some evidence the UK was close to that despite testing pretty heavily compared to the rest of the world e.g. https://www.news-medical.net/news/20210215/Only-2525-of-SARS... (I seem to recall the BBC reported on this at the time, but finding their old Covid-19 coverage again is basically impossible.)
Remember, fully asymptomatic infections aren't the only problem, there are also infections that technically have symptoms but they're too vague, commonplace and non-specific to lead to people getting tested.
A half of people I know, who self-reported covid-like symptoms from mild to very severe (n=20) had their tests negative. This is Moscow, Russia. They are not counted in official statistics.
Norway lacked test capacity like everyone else early during the pandemic. We did antibody tests later to see what we had missed.
Turns out in spite of all asymptomatic cases etc the guesstimates were fairly good.
Now Norway is an extremely rich country and healthcare is (generally) excellent here, but if asymptomatic cases were really widespread we should have seen some non trivial percentage showing up in the antibody tests that we weren't aware of earlier.
Of course it matters. If you have millions of people taking public transport every day vs people driving in individual cars, makes a huge difference in exposure.
The only way to really know, would have been have worldwide, forced testing of every single person, weekly.
EG billions of test per week.
There were no tests at the start, not enough worldwide testing ability for the first 6 months, and once capacity existed, generally only people who felt sick were tested.
And that's in rich nations.