Data regarding national income in 2011: United States Census Bureau, “Selected Population Profile in the United States 2009-2011 American Community Survey Three-Year Estimates” (Table S0201)

States’ Votes on the Equal Rights Amendment: About.com Women’s History

States with State-Level Equal Rights Amendments: League of Women Voters of the Fairfax Area, “Ratification States in the States and State ERAs” .pdf

Historic Data on Income by State and Sex: US Census Bureau, Historic Income Tables: People, “Table P-36. Full-Time, Year-Round Workers by Median Income and Sex” and “Table P-37. Full-Time, Year-Round Workers by Mean Income and Sex”, “All Races” table used for both