At the Osaka G20 summit in Japan, world leaders are grappling with one of the most challenging issues humanity faces today: We’re not getting any younger.

Last year, for the first time in human history, the number of people on Earth aged 65 or older outnumbered children under five, according to a recent United Nations report. People over 65 are now the world’s fastest-growing age group. Three decades from now, one-quarter of the population in Europe, the United States and Canada will be over 65.

“Historically low levels of fertility combined with increased longevity ensure that populations in virtually all countries and areas are growing older,” the report observed.

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Aging populations place an enormous burden on the young, because there are fewer of them every year in relation to the old – fewer taxpayers to prop up health and pension plans, fewer consumers to drive a domestic economy, fewer children to offer comfort and support for elderly parents.

In terms of what’s known as the potential support ratio, Japan has the oldest population on Earth. After the Second World War, there were 12 people of working age (15-64) for every retired person (65 and older); today, there are only two. In India, the ratio is 10; in Canada, four.

As this year’s hosts, Japan has put the issue of aging as a societal risk on the Group of 20 agenda.

“We are facing many challenges as an aging society,” Kimihiro Ishikane, Japan’s ambassador to Canada, explained in an interview. “And we are sure many countries will be facing similar challenges, now or in the near future.”

The phenomenon of societal aging, once begun, can never be reversed. The strains are more serious every year in developed countries. And with fertility rates falling and life expectancy increasing from Brazil to Indonesia, societal aging is becoming an issue in the developing world, too.

To combat the growing labour shortages resulting from so few young workers, the Japanese government has sought to increase female participation in the work force through improved support for parental leave and child care. Government and industry invest heavily in robotic technology. And Japan is increasingly making use of temporary foreign workers.

However, such measures are “easy to say, but difficult to implement,” Mr. Ishikane observed.

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One of the most difficult measures of all to implement, in both Japan and Canada, is convincing workers to delay retirement. Sixty-five-year-olds are generally healthier today than they were a generation or two ago. Persuading them to stay in the work force would ease pension pressures and labour shortages.

But the move by the Conservative government of Stephen Harper to raise the retirement age to 67 was so unpopular that the Liberals promptly scrapped the measure when they came to power.

Canada does have one big advantage over Japan, in that this country continues to welcome large numbers of immigrants, including foreign students who are encouraged to stay on as permanent residents. Although there are abuses, such as The Globe discovered in its recent investigations, bringing young immigrants to Canada is a relatively cheap and easy counterbalance to societal aging.

There are those who would close the doors to new Canadians, while promoting policies that encourage parents to have more children. But such policies to bring fertility rates back up to 2.1 children per woman – replacement level fertility – have failed everywhere they have been tried.

We are only going to get older, owing to declining fertility and the latest medical advances. By 2050, there will be more people 65 and older than there are people under 25. Someone born today in Canada may lack for siblings, but by the time she reaches her 90s, she may well have several centenarian friends.

Different countries approach the question of aging differently, depending on attitudes toward family, elders, children and foreigners. “It depends on what kind of social structure you have,” Mr. Ishikane said. Developing societies face even greater challenges than developed ones, because they lack the resources to establish social safety nets for the elderly. “Each country has its own challenge.”

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But they all have one challenge in common, he adds. “All those countries are aging, sooner or later.”

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