Urban Growth: Trends Vs. Noise

This paper carries out a comparative analysis of the so-called classical urban growth models and ramdon urban growth models in order to explain their explanatory capabilities about urban growth and cities size distribution. The process of innovation through experimentation embedded in the classical urban growth models has shed new ligth to explain the coexistence of both diversified and specialized cities and role that diversified cities play as “nursery cities” by facilitating experimentation (Duranton and Puga, 2001). Classical urban growth models do not naturally generate the Zipf’s law (the rank-size rule for cities), whereas ramdon urban models provide a number of explanations for this key stylized fact. The theoretical foundations of both kind of models and their degree of compatibility are also examined. An exact statement of the conditions under which both type of models may be compatible is also needed.