The world is aging so fast that most countries are not prepared to support their swelling numbers of elderly people, according to a global study out today by the United Nations and an elder rights group.

The report ranks the social and economic well-being of elders in 91 countries, with Sweden coming out on top and Afghanistan at the bottom. It reflects what advocates for the old have been warning, with increasing urgency, for years: Nations are simply not working quickly enough to cope with a population graying faster than ever before. By the year 2050, for the first time in history, seniors older than 60 will outnumber children under the age of 15.

Truong Tien Thao, who runs a small tea shop on the sidewalk near his home in Hanoi, Vietnam, is 65 and acutely aware that he, like millions of others, is plunging into old age without a safety net. He wishes he could retire, but he and his 61-year-old wife depend on the $50 a month they earn from the tea shop. And so every day, Thao rises early to open the stall at 6 a.m. and works until 2 p.m., when his wife takes over until closing.

Thao’s story reflects a key point in the report: Aging is an issue across the world. Perhaps surprisingly, the report shows that the fastest aging countries are developing ones, such as Jordan, Laos, Mongolia, Nicaragua and Vietnam, where the number of older people will more than triple by 2050. All ranked in the bottom half of the index.

The Global AgeWatch Index (www.globalagewatch.org) was created by elder advocacy group HelpAge International and the U.N. Population Fund in part to address a lack of international data on the extent and impact of global aging. The index, released on the U.N.’s International Day of Older Persons, compiles data from the U.N., World Health Organization, World Bank and other global agencies, and analyzes income, health, education, employment and age-friendly environment in each country.

The index was welcomed by elder rights advocates, who have long complained that a lack of data has thwarted their attempts to raise the issue on government agendas.

“Unless you measure something, it doesn’t really exist in the minds of decision-makers,” said John Beard, Director of Ageing and Life Course for the World Health Organization.

The report fits into an increasingly complex picture of aging and what it means to the world. On the one hand, the fact that people are living longer is a testament to advances in health care and nutrition, and advocates emphasize that the elderly should be seen as a resource. On the other, many countries still lack a basic social protection floor that provides income, health care and housing for their senior citizens.

Afghanistan, for example, offers no pension to those not in the government. Life expectancy is 59 years for men and 61 for women, compared to a global average of 68 for men and 72 for women, according to U.N. data.

Prosperity in itself does not guarantee protection for the old. The world’s rising economic powers — the so-called BRICS nations of Brazil, Russia, India, China and South Africa — rank lower in the index than some poorer countries such as Uruguay and Panama.

However, the report found, wealthy nations are in general better prepared for aging than poorer ones. Sweden, where the pension system is now 100 years old, makes the top of the list because of its social support, education and health coverage, followed by Norway, Germany, the Netherlands and Canada. The United States comes in eighth.