People in Japan continue to outlive those in other countries, marking the world’s longest average life expectancy of 83.7 years, according to the latest World Health Organization report released Wednesday.

The World Health Statistics 2017, covering data from 194 countries, show that the nation’s life expectancy at birth has been ranked No. 1 for more than 20 years, followed by Switzerland, Singapore, Australia and Spain — with averages ranging from 82.8 to 83.4 years.

The size of the economy seemed to have little effect on a nation’s longevity, with the average life expectancy in the U.S. at 79.3 years and China at 76.1.

Women in Japan lived longer than their male counterparts. At 86.8 years, they ranked first in the world, trailed by women in Singapore at 86.1 years, South Korea and Spain at 85.5, and France at 85.4.

Japanese men, meanwhile, ranked sixth, with a life expectancy of 80.5 years. Swiss men lead the category at 81.3 years, followed by Icelanders at 81.2, Australians at 80.9, Swedes at 80.7 and Israelis at 80.6.

That compares with the global average of 69.1 years for men, 73.8 years for women and 71.4 for both sexes.

The reasons for Japan’s longevity have been a source of debate, but due to genetic, social and lifestyle issues it is hard to find a single causal factor. The health ministry cites the nation’s high living standards and medical advances. Some experts also point to diet and the nation’s universal and accessible health care system.

The government in recent years has focused on extending the “healthy life expectancy,” which refers to the number of years people live in full health. According to the WHO report, Japan also leads the world in the average healthy life expectancy, at 74.9 years, followed by Singapore’s 73.9 years and South Korea’s 73.2 years.

But it also means that, on average, the Japanese spend their last 8.8 years living in ill health, many mobility impaired or bedridden. The government is aiming to reduce unhealthy years in order to improve the quality of life and also to tame the rise in medical and nursing care costs.