The long way to tipperary: City size and worldwide urban population trends, 1950-2030

A comparative investigation of population growth gives accurate information on urban transformations at local and regional scales. A comprehensive understanding of future trends in global urbanization may benefit from a long-term analysis of city size, a key variable influencing population growth. Taken as a dynamic feature of urban systems, the relationship between city size and population growth was investigated in 1857 agglomerations (> 300,000 inhabitants in 2014) of 155 countries across the globe between 1950 and 2030. Despite important regional differences, an inverse relationship between population growth and city size was observed up to the late 1990s. Slowdown of population growth during more recent decades and higher spatial heterogeneity in population trends may reflect a transition from high to low fertility, ageing and spatially diversified migration patterns. Present (and future) population trends in urban agglomerations (will) overlap only partly with those observed in the past, being more unpredictable over time and space. Analysis of changes in the relationship between city size and population growth definitely contributes in the debate about the future development of urban agglomerations worldwide.