Continuous vs. Discrete Urban Ranks: Explaining the Evolution in the Italian Urban Hierarchy over Five Decades
通过分析1971至2011年意大利城市等级的变化，发现城市排名的微小连续变化与大幅离散跳跃的驱动因素不同，高级城市功能的存在预测了城市在离散等级中的大幅跃升。
The reasons for changes in ranking within urban systems are a matter of a wide and long debate. Some focus on a continuous and smooth ordering of cities by their size within the urban system, in the tradition of Zipf’s law. Others focus on discrete, discontinuous ordering, as cities take on functions at different levels, such as specialized market places or high-level education, in the tradition of Christaller. We enter the debate by empirically evaluating whether the same determinants explain continuous or discrete changes in urban ranks in the evolution of the Italian urban hierarchy over the years 1971 to 2011. We empirically show that small, continuous changes of cities’ ranks have different drivers than large, discontinuous leaps. The presence of high-level functions in a city predicts major leaps across discrete ranks. Results are robust to the use of an instrumental variable strategy based on a shift–share argument.