Wisconsin). PhD dissertation, University of Wisconsin-Madison, 1985. Marvin Wachman, Social-Democratic Party of Wisconsin, 1897-1910. Urbana: University of Illinois Press, 1945. Frank P. Zeidler, Ninety Years of Democratic Socialism: A Brief History of the Socialist Party USA.'' Milwaukee: Socialist Party USA, 1991. SDPW average paid memberships {| class="wikitable" border="3" |- ! Year ! Average Paid Membership ! Exempt Members ! National SPA Membership |- ! align="center" | 1901 | align="center" | | align="center" | n/a | align="center" | 4,759 paid (of 7,629) |- ! align="center" | 1902 | align="center" | 370 | align="center" | n/a | align="center" | 9,949 |- ! align="center" | 1903 | align="center" | | align="center" | n/a | align="center" | 15,975 |- ! align="center" | 1904 | align="center" | | align="center" | n/a | align="center" | 20,763 |- ! align="center" | 1905 | align="center" | | align="center" | n/a | align="center" | 23,327 |- ! align="center" | 1906 | align="center" | | align="center" | n/a | align="center" | 26,784 |- ! align="center" | 1907 | align="center" | | align="center" | n/a | align="center" | 29,270 |- ! align="center" | 1908 | align="center" | | align="center" | n/a | align="center" | 41,751 |- ! align="center" | 1909 | align="center" | 1,831 | align="center" | n/a | align="center" | 41,470 |- ! align="center" | 1910 | align="center" | | align="center" | n/a | align="center" | 58,011 |- ! align="center" | 1911 | align="center" | | align="center" | n/a | align="center" | 84,716 |- ! align="center" | 1912 | align="center" | | align="center" | n/a | align="center" | 118,045 |- ! align="center" | 1913 | align="center" | | align="center" | | align="center" | 95,957 |- ! align="center" | 1914 | align="center" | | align="center" | | align="center" | 93,579 |- ! align="center" | 1915 | align="center" | | align="center" | | align="center" | 79,374 |- ! align="center" | 1916 | align="center" | 3,092 | align="center" | | align="center" | 83,284 |- ! align="center" | 1917 | align="center" | 3,694 | align="center" | | align="center" | 80,379 |- ! align="center" | 1918 | align="center" | 5,160 (first 6 mos.) | align="center" | | align="center" | 82,344 |- ! align="center" | 1919 | align="center" | | align="center" | | align="center" | 104,822 |- ! align="center" | 1920 | align="center" | | align="center" | | align="center" | 26,766 |- ! align="center" | 1921 | align="center" | | align="center" | | align="center" | 13,484