[Fibrinogen concentrates and collagen sponges for tissue adhesion].

Abstract

We propose a framework that specifies the process of economic development as\nan evolutionary branching process of product innovations. Each product innovation\nprovides a growth opportunity for an existing firm or a new firm, and for an existing city\nor a new city. One can then obtain both firm size and city size distributions as two\naggregates resulting from a single evolutionary process. Gains from variety at the firm\nlevel (economies of scope) and the urban level (Jacobs externalities) provide the\ncentral feedback mechanism in economic development generating strong path\ndependencies in the spatial concentration of industries and the specialization of\ncities. Gains from size are also expected, yet these are ultimately bounded by\nincreasing wages. The contribution of our framework lies in providing a microfoundation\nof economic geography in terms of the interplay between industrial\ndynamics and urban growth. The framework is sufficiently general to investigate\nsystematically a number of stylized facts in economic geography, while at the same\ntime it is sufficiently flexible to be extended such as to become applicable in more\nspecific micro-contexts. A number of extensions related to the concepts of knowledge\nspillover and lock-in, are also discussed.