Rendita fondiaria e dinamica urbana: le determinanti dello sviluppo urbano nel caso italiano

Urban dynamics was studied during the eighties in terms of the so-called ‘urban life cycle theory’ which was launched by the Vienna group within the CURB (costs of urban growth) project. The main elements of this theory, as well as its limits, are already well known. It provides an elegant way of describing urban trends and dynamics by interpreting them as the result of a natural process of physical diffusion of urban population from core areas to the periphery. The opposite movement, from periphery to core, is explained on the other hand by the existence of scale diseconomies. However, some aspects remain unresolved: for example, is there a city size threshold at which the process of decentralisation starts? At what city size do scale economies become scale diseconomies? At what point in time does this happen? Should we expect cities like Milan and Rome to grow to the size of London and Paris before they start to decline? Many empirical analyses have proved the existence of an optimal city size through the measurement of economies or diseconomies of scale, generally applied either to the costs of urban services or to elegant econometric estimates of urban and sectoral production functions. But, unfortunately these studies have never produced a common result, and have often been subject to criticism for their restrictive hypotheses. The aim of the present paper is twofold. First of all, we describe urban dynamics in Italy through an indicator of urban costs and advantages, i.e. urban rent. House prices are in fact a good indicator of the attraction of an urban area, as they are synthetic and avoid a time lag between the occurrence of phenomena such as demographic change, and the availability of data to capture these phenomena. This study is based on the idea that the difference in house prices between large and small cities is a measure of their relative attraction (and thus their relative location advantage). The second aim is to highlight the determinants of this urban dynamics, and especially to understand whether urban development patterns are similar in cities of different size. For this second issue, the paper enters the debate on the existence of an optimal city size for all cities and draws attention to other possible determinanats of urban development.