Paul Kershaw loves his 72-year-old mother and his 101-year-old grandmother.

But they represent a growing challenge for the country, and Kershaw, 42, will be counting on younger age groups to protect and support the services that seniors need as Canada bears witness to a historic greying of its population.

The next batch of numbers from the 2016 census, due Wednesday, is expected to show that thanks to aging baby boomers, there are as many seniors in Canada as young people, if not more -- the first time in Canadian history that has been the case.

There is also likely to be a jump in the number of centenarians, including Kershaw's grandmother, showcasing another trend the age and sex data from Statistics Canada will confirm: Canadians are not only getting older, but also living longer.

Wednesday's release ought to trigger a national discussion about the challenges Canada faces in the coming years, said Kershaw, an associate professor in the school of population and public health at the University of British Columbia.

Those include how best to serve the growing needs of the elderly, how to make sure the younger generations don't get swamped in the wake of the boomers and how far government policy should go when it comes to keeping people in the workforce.

Federal spending on seniors' benefits is expected to climb from $51.1 billion this fiscal year to $63.7 billion by 2022 -- a $12.6-billion increase that easily outstrips a decade of planned Liberal spending on a national housing strategy or child care.

That increase, about 5.7 per cent a year, also dwarfs even the most bullish economic growth projections, warned Kershaw, the founder of the group "Generation Squeeze," which seeks to engage young people in politics.

"We still need to have this important conversation in Canada about the degree to which we are using the vast majority of our economic growth each year to be covering the costs of an aging population."

Demographics, by their very nature, are slow-moving; Wednesday's numbers will yield few surprises, since people age and die in predictable patterns. But their slow-moving and predictable nature makes them easy to ignore, demographers warn.

The figures will add another dimension to the portrait of Canada the five-year census began painting earlier this year with the release of the country's overall population figures. Additional layers will be added throughout the year, including family, household and marital status data in August; immigration and Aboriginal Peoples numbers in October; and figures detailing education, jobs and work patterns in November.

On Wednesday, experts and policy-makers will be looking for clues about which age cohorts are growing, which are on the decline, where various age groups are choosing to live and the type of housing they prefer.

Wednesday's numbers are expected to show that on census day 2016, which was May 10, the percentage of those over 65 was roughly equal to the percentage of those aged 15 and under.

Such a shift would be a dramatic and historic swing from the height of the baby boom 50 years ago, when seniors comprised less than eight per cent of the population and the youngest cohort was 34 per cent, said Doug Norris, chief demographer at Environics Analytics.

Nonetheless, the census figures are expected to show Canada remains one of the youngest countries in the G20, Norris said.

"Canada is aging more than many other countries, but we're still at a lower level, even with that faster change, than certainly most European countries," said Norris, who spent three decades at Statistics Canada.

"There may be some things we can learn from countries that are dealing with the kind of population we're going to face in another decade or two."

Some of those lessons are already being put into practice: urban planners are thinking about how to build a city that allows Canadians to age in place by staying in their homes as long as possible. At the same time, businesses and governments are thinking about ways to keep people in the workforce longer, including incentives for individuals to retire later than 65 and incentives for businesses to hire young and old.

With more Canadians living longer, older baby boomers are finding themselves caring for elderly parents, adult children and grandchildren, said Michael Haan, an associate professor in the school of sociology at Western University in London, Ont.

The trend may carry over to their children, Haan added: the boomers are expected to be one of the longest-lived generations of Canadians ever.

"This is really incredible, and it's unprecedented historically because people have never lived this long."