By dissecting how cities and their economies emerge and grow, Jacobs cast new light on the nature of local economies. She contested the assumptions that cities are a product of agricultural advancement; that specialized, highly efficient economies fuel long-term growth; and that large, stable businesses are the best sources of innovation. Instead, she developed a model of local economic development based on adding new types of work to old, promoting small businesses, and supporting the creative impulses of urban entrepreneurs. [Project for Public Spaces](https://www.pps.org/reference/jjacobs-2/)