WORLD MIGRATION REPORT 2015 Migrants and Cities: New Partnerships to Manage Mobility
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and comparing “functional urban areas” (OECD, 2012) is one such example based on relative economic function rather than administrative boundaries. It uses population density to identify urban cores and travel-to-work flows to identify the hinterlands whose labour market is highly integrated with the cores. This may allow better understanding of the changes in settlement form and functioning in relation to changing social, economic and environmental complexity and especially in relation to other cities of different size and functions. However, the methodology is limited to the OECD countries and has not yet factored in migration or mobility. The present report follows the general approach to cities of the United Nations taking into account national definitions and their size differentiation (UN DESA, 2014): • Megacities with more than 10 million inhabitants are home to only about one in eight of the world’s urban dwellers. Today the number of megacities has nearly tripled to 28 from a mere ten in 1990, with 453 million inhabitants, accounting for 12 per cent of the world’s urban dwellers. • Large cities with 5 to 10 million inhabitants account for a small, but growing proportion of the global urban population. In 2014, just over 300 million people lived in large cities, currently accounting for eight per cent of the urban population of the world. • One in five urban dwellers worldwide lives in a medium-sized city with 1 to 5 million inhabitants. The global population living in medium-sized cities nearly doubled between 1990 and 2014, and is expected to increase by another 36 per cent between 2014 and 2030, growing from 827 million to 1.1 billion. • The number of people living in cities of between 500,000 and 1 million inhabitants is expected to hold only around 10 per cent of the global urban population. In 2014, close to one half of the world’s urban population lives in settlements with fewer than 500,000 inhabitants. While this proportion is projected to shrink over time, by 2030 these small cities and towns will still be home to around 45 per cent of urban dwellers. Global urban population growth is propelled by the growth of cities of all sizes, as the UN DESA World Urbanization Prospects, 2011 Revision report mentioned above noted. Migration does contribute to urbanization, although the precise characteristics of migration flows remain inadequately studied. As such, cities of all sizes, municipalities, small towns, and even rural areas with their growing linkage to urban centres, are dealt with in the present report. As migrants, especially international migrants, tend to gravitate toward cities rather than small towns, medium-sized and large cities are discussed more often than other localities in this report. (See Global map: Migrants and cities: At a glance.)