Los Angeles exemplifies urbanization economies in that it has no single dominant industry, yet continues to grow. Firms which locate in Los Angeles benefit from the common resources and large labor pool found in the city. Common resources such as roads, buildings and power supply benefit firms in cities regardless of their industry. Also, firms have better access to labor by locating in cities. The urban environment creates positive externalities that benefit several different industries. Jane Jacobs is often credited with the idea that urban diversity and a city’s size leads to agglomeration economies. However, Marshall’s (1920)[4] discussion of urban diversity predates her work.[5]