working class had the right to vote, become common only in the 1930s and 1940s. Causes There is considerable debate about the factors which affect (e.g., promote or limit) democratization. Economic, cultural, and historical factors have been cited as impacting on the process. So too have historical and international factors. Moreover, some arguments are more structural in nature, while others focus on leadership and agency. It is useful to order the various arguments under different headings. Economic factors Economic development and modernization theory Scholars such as Seymour Martin Lipset; Carles Boix and Susan Stokes, and Dietrich Rueschemeyer, Evelyne Stephens, and John Stephens argue that economic development increases the likelihood of democratization. Initially argued by Lipset in 1959, this subsequently been referred to as modernization theory. According to Daniel Treisman, there is "a strong and consistent relationship between higher income and both democratization and democratic survival in the medium term (10–20 years), but not necessarily in shorter time windows." Robert Dahl argued that market economies provided favorable conditions for democratic institutions. A higher GDP/capita correlates with democracy and some claim the wealthiest democracies have never been observed to fall into authoritarianism. The rise of Hitler and of the Nazis in Weimar Germany can be seen as an obvious counter-example, but although in early 1930s Germany was already an advanced economy, by that time, the country was also living in a state of economic crisis virtually since the first World War (in the 1910s), a crisis which was eventually worsened by the effects of the Great Depression. There is also the general observation that democracy was very rare before the industrial revolution. Empirical research thus led many to believe that economic development either increases chances for a transition to democracy, or helps newly established democracies consolidate. One study finds that economic development prompts democratization but only in the medium run (10–20 years). This is because development may entrench the incumbent leader but make it more difficult for him deliver the state to a son or trusted aide when he exits. However, the debate about whether democracy is a consequence of wealth, a cause of it, or both processes are unrelated, is far from conclusive. Another study suggests that economic development depends on the political stability of a country to promote democracy. Clark, Robert and Golder, in their reformulation of Albert Hirschman's model of Exit, Voice and Loyalty, explain how it is not