4% is the number after magic gubmint number massaging. I think it is all in the gubmint definition of unemployed and has little or nothing to do with the actual number of people not working. If there are over 90,000,000 working age Americans not in the labor force the true UE number has to be closer to 20% than 4%.
I don’t disagree with what you’re saying. However, if a portion of that 90M (is that a correct # by the way) are people who do not want a job (i.e. my friend the stay at home Dad) then the number should revise lower.
That said, we agree it’s not 4%. And likely never will be that low again. The US has become a Service Economy where it used to be mostly a Manufacturing Economy. A lot of the unemployed need to be re-trained because those jobs aren’t coming back. Not in the lifetime of the employees that were phased out.