This paper is a contribution to the empirical literature on city size distribution. It is based on Zipf’s law and uses evidence provided by Spanish municipalities throughout the 20th century. The paper begins by criticizing the most frequently used database for municipal population and offers an alternative source of the data, one that is homogenous for all the census years of the 20th century and the year 2001. It then examines the concept of “city” before finally opting for the Urban Area as proposed by the Ministry of Public Works in its Atlas de Áreas Urbanas, which (in some cases) exceeds municipal boundaries. Starting from a generalization of the Pareto distribution, we carry out a formal statistical test of the Zipf’s law. We also offer the results of estimating the rank-size rule using the latest statistical techniques. We are unable to reject Zipf’s law generally for the concept of “city” that we use.

Key words: Population, Municipalities, Census, Agglomeration, Metropolitan Areas.
JEL Classification: J10, J11.