Unlike ground ambulances, whose growth is controlled in many states, medical helicopter operators face few such limits. Bases have proliferated, with wide differences in coverage. Kentucky has 26 medical helicopters to Canada's 20, even though Canada has nearly 30 million more residents.

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SOURCE: Centers for Medicare and Medicaid Services, Washington Post analysis
GRAPHIC: Kat Downs, Gil Gaul, Lauren Keane - The Washington Post

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