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The world's worst humanitarian crisis, by the numbers
Displaced Yemenis sit under a makeshift shelter at a camp for internally displaced persons.
Displaced Yemenis sit under a makeshift shelter at a camp for internally displaced persons. Photo: STR / AFP / Getty Images

Warfare, severe food shortages and disease are devastating Yemen, already one of the world's poorest countries. The U.N. has called the situation the "largest humanitarian crisis in the world," and U.N. Ambassador Nikki Haley said recently that "no one should ever have to live the way the people of Yemen are living."

Why it matters: The U.N. estimates that more than 22 million Yemenis are in need of humanitarian assistance. The population of Yemen is 27 million.