Megacities, the World’s Largest Cities Unleashed: Major Trends and Dynamics in Contemporary Global Urban Development

•Cities around the world keep growing and megacities (10 million+) are unleashed.•There is a clear divergence between “mega-local cities” and “mega-global cities”.•An empirical relationship found: one megacity per 100 mil population in a country.•Powerful “internal” force at work: the largest cities lead to polarization growth.•Key external drivers of urban growth: transport, I.T., finance & business services. In this study we ask two basic questions: will the megacity trend continue into the immediate and long-term future and why do more and more people continue to concentrate in the world’s biggest cities? Based on the UN dataset of all cities in the world with population 750,000 and a number of other datasets, and with an innovative application of the Gini-coefficient, this study explores the on-going trends and patterns of contemporary human urban settlement over the past half century, particularly the phenomenal growth of megacities (10 million+) and their powerful “internal” and “external” driving forces. Key findings: (1) Cities around the world are becoming bigger and bigger, and megacities, the world’s biggest cities, are unleashed, with a clear divergence between “mega-global cities” with more powerful and advanced business services sectors or international financial centers, and “mega-local cities” that do not; (2) an empirical “megacity relationship” whereby a country or territory will potentially have one megacity for every 100 million people in the country with the prime city population largely controlled by country population; (3) powerful “internal” forces at work: the prime city of each country tends to dominate their respective urban structures and occupy an increasingly-larger share of national population, giving an endogenous account as to why some cities, particularly the largest cities, become bigger and bigger; (4) major “external” forces: among the tested 20 and aggregated 5 variables, IT, and finance and business sectors are the key “external” factors driving the growth of cities and megacities, transforming “mega-local cities” to “mega-global cities”; (5) improved transport and telecommunication networks are also strong external factors driving megacity growth, in contrast to common perceptions and most of the existing literature.