Please explain this reasoning? Do you have any direct evidence this would be the case, in a general sense and not just personally? Income taxes in the US were

Please explain this reasoning? Do you have any direct evidence this would be the case, in a general sense and not just personally? Income taxes in the US were the highest they've ever been in the 50s, 60s, and 70s and those were some of the most productive decades in this country's history.