In 1932, Geiger wrote an analysis of the classes in Germany. The analysis was based on an empirical study of social stratification. In his analysis of the data, he classified the population into five groups, more complex than capitalists and proletariat as used by Marx, to determine the objective economic criteria of class. Here, he made the distinction between objective and subjective forms of social class analysis including objective social status and subjective class consciousness, respectively. He distinguishes the "old" middle class of farmers, artisans, and merchants from the "new" middle class of well trained professionals. Geiger saw the new salary-earning middle class as a sort of evolution of the proletarian class. He also believed that the middle class was more susceptible to new extremist ideologies like Nazism because it has a defensive and vulnerable position due to its lack of secure class identity. He elaborated on these ideas about the middle class in Klassesamfundeti Stobegryden (Class Society in the Melting Pot), after World War II. In London, Geiger and David Glass formed a subcommittee on social stratification and mobility and together they started a comparative study of international mobility and stratification.