Thank you [USER=38109]@Cataceous[/USER] for your thoughtful point.
I wonder if one reason testosterone levels have been falling in recent decades is perhaps because it is actually healthier to have slightly below average levels of testosterone. No doubt there are negative factors causing the fall in testosterone (e.g., obesity), but perhaps also because it has become evolutionary disadvantageous to have levels of 800/900+.
I think one day we will look back and realize how unhealthy it was to aim for “high normal” (800-1000) testosterone levels in the same way we look back today and realize how unhealthy it was to manipulate estrogen into the “low normal” range (10-15).