More than a quarter of Vietnam’s residents live in areas likely to be subject to regular floods by the end of the century. Four percent of China’s residents — 50 million people — live in the same kind of areas. Across the globe, about one person in 40 lives in a place likely to be exposed to such flooding by the end of the century, absent significant changes.

These figures are the result of a new analysis of sea levels and flood risk around the world, conducted by Climate Central and based on more detailed sea-level data than has previously been available. The analysis offers country-by-country estimates for populations at risk of regular flooding, accounting for a range of potential emissions reductions and for variations of sea level sensitivity to climate change.

Globally, eight of the 10 large countries most at risk are in Asia. The Netherlands would be the most exposed, with more than 40 percent of its country at risk, but it also has the world’s most advanced levee system, which means in practice its risk is much lower.

Some countries in Asia may choose to emulate the Dutch system in coming decades, but some of the Asian nations are not wealthy and would struggle to do so.