The nineteenth century witnessed an unprecedented degree of urbanization, an increase in urban population growth relative to population growth generally. One of the chief consequences of this growth was class segregation, as the bourgeoisie and upper classes were forced to inhabit the same confined space as workers. Significantly, this had opposed effects in Europe, where the working classes typically inhabit the periphery of cities, and the United States, where they are most often in the city center itself. The growth of cities was accompanied by a high-pitched rhetoric of disease and decay, as the perceived hygienic problems of concentrated urban populations were extrapolated to refer to the city itself as a biological organism. The Baron Haussmann's reconstruction of Paris under the Second Empire is a classic example of the intertwinement of urban development, capitalism and state power.