The secret ballot is one of the cornerstones of democracy. We contend that the historical process of modernization caused the switch from open to secret ballot with the underlying mechanism being that income growth, urbanization, and rising education standards undermined vote markets. We undertake event history studies of ballot reform in Western Europe and the U.S. states during the 19th and 20th centuries to establish that modernization was systematically related to ballot reform. We study electoral turnout before and after ballot reform among the U.S. states and British parliamentary constituencies to substantiate the hypothesis that modernization reduced the volume of trade in the vote market.