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Globally, cities are on the rise: the world’s population is now more than 50% urban, and rapidly increasing. But how exactly does the growth of cities play out in practice? Migration patterns have for so long been difficult to track by official data collection agencies such as census bureaus. But now, we’re getting a clearer picture of this phenomenon from another source: Facebook.

In a recent study published by the Facebook Data Science Team, researchers compared users’ listed hometowns to their current cities of residence. They then used that data to tease out “coordinated migrations”: statistically significant groups of specific parings between home cities and current cities.

They found that most of the fastest growing cities were in the developing world. Topping the list were Lagos, Istanbul, Bogotá, Bangkok, and Accra. They also found that in most cases, coordinated migrations occurred within the same country, though transnational migrations were also represented.

Looking at the maps produced by this study, a clear “hub and spoke” pattern emerges, where large centers become the nucleus of migration from surrounding areas.  This is particularly pronounced in places such as Africa, India, and Latin America, where the population is rapidly shifting from rural to urban. But even in countries in Europe and North America, where the population has already urbanized for the most part, the same pattern can be seen to a lesser extent.

Facebook map

It should be noted that these results may not be perfect. Even though Facebook has 1.2 billion users, roughly 15% of the world’s population, there are still over 6 billion who don’t use it. And many of those people are likely not to have access to internet, in many cases because they remain in rural areas. As a result, this study may exaggerate the rate at which people are moving to cities, as people less likely to move to cities are also less likely to use Facebook. Nonetheless, other indicators (such as this report by the WHO) show that in general, the portrayal given by this study is representative of actual trends. What’s more, it gives us some indication of how they play out in practice, without the difficulty of collecting data manually.

This study is proof positive that cities are playing an increasingly important role in the world’s future. And for the urban planning community, this is both good and bad news. Living in cities potentially means that people will be able to live better lives in a sustainable way, since distances to jobs and services are reduced. But it also means that cities will have to make sure to provide those essential services such as running water, electricity, and waste management – not an easy task. This new study is an affirmation of the importance of ensuring the world’s cities run smoothly and sustainably. The future depends on them.

Drew Reed is an online media producer and community activist specialising in sustainable transportation. He lives in Buenos Aires.

Images via Ksayer1 and Isaac Mo