1. Older people taking retirement early when the pandemic hit.
2. People in service/public-facing industries leaving for jobs that could be done remotely, or going back to school.
3. Several hundred thousand working age people dying from COVID.
It all boils down to survival of the fittest and history repeatedly shows and the the US Govt & US Mil demonstrates, violence always wins the day.
a. The official number is ~254,000 (in the USA) which is certainly a major over-estimate. True number is certainly far less.
b. Employees who died or retired don't count as resigned.
Can you point me to your source(s) indicating the lower number you’re referring to?
Then summing the 18-65 buckets (working age).