"Head of household", traditionally male - wifey stayed at home; fewer households can avail themselves of the one paycheck nowadays. The post-WWII prosperity, helped by the pre-war rise of labor unions, made it possible for unionized blue collar workers to move from tenement-dweller to homeowner, or from Ralph Kramden to Archie Bunker. That rising tide lifted many non-unionized boats as well, something to think about in this age of a demonized Left and sweatshop addiction.