19 photos show what life is like in the world's most crowded cities

Mohammad Ponir Hossain/Reuters

Urbanization is taking over the world.

By the year 2050, 70% of the world will live in cities, according to the Population Reference Bureau.

One of the most striking ways to see this growth is through the lens of population density, or the way statisticians measure congestion.

The densest cities grapple with unique challenges. They fight for resources, like housing and personal space, and they put infrastructure to the test.

Here's just a taste of what life is like.

This is New York City, the densest city in the US. One square mile contains more than 27,000 people. Claustrophobic as it may seem, it barely stacks up against the world's most crowded cities.

Luciano Mortula/Shutterstock

Source: NYC Population

Consider Manila. With a population density of 107,000 people per square mile, it's the most crowded city in the world.

Erik de Castro/Reuters

Manila's fertility rate is 3.1 children per woman. Experts predict the population will double by 2025, despite fears the city's infrastructure can't sustain the boom.

John Javellana/Reuters

Source: World Population Review

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