Public vs Private Jobs

A Dish reader asserted that the "idea that public employees make less than those in the private sector is a myth that needs to die." Drum responds:

[Is] this actually true? In the upper reaches of management, it obviously isn't. Mid-level and executive level managers often make half as much as comparable private sector managers. (Or less.) And although rich pension deals make headlines, it's not clear how widespread they really are. More generally, though: do ordinary workers (clerks, school teachers, construction workers, etc.) make as much as their private sector counterparts? Or more? And where could we go to find out?