OTTAWA — Colin Basram is having growing pains. In some ways a victim of his own success, the mayor of Kelowna has been struggling in recent years to rein in his city as it slowly spreads across the B.C. interior, testing his ability to provide core municipal services and build badly needed infrastructure. Nor is the city's middle-aged spread at all unique, according to the 2016 census data released Wednesday: Canada's population of 35.15 million is settling in the bigger cities, ensuring they and their suburban neighbours keep growing, while small cities get smaller. The three biggest metropolitan areas in the country — Toronto, Montreal and Vancouver — are now home to more than one-third of all Canadians with a combined population of 12.5 million, with almost one half living in Toronto and its suburban neighbours, the data shows. Canada is once again the fastest growing country in the G7, Statistics Canada says in the first of what will be seven tranches of 2016 census data to be released over the course of the year. Wednesday's release focused on population and dwellings; the next one, in May, will be focused on age and sex. The latest figures also show that the once yawning gulf in growth rates between the spreading suburbs and their urban centres has continued to narrow, with young professionals and aging baby boomers alike opting for the downtown-condominium life. The census shows that 82 per cent of Canadian population live in large and medium-sized cities across the country, one of the highest concentrations among G7 nations. Immigration has driven that change with new arrivals settling in urban centres as opposed to rural communities.

"The municipalities located on the edge of the (census metropolitan areas) are growing faster than the municipalities located (in the centre) of the census metropolitan area,'' said Laurent Martel, director of the demography division at Statistics Canada. "Also the rural areas located outside the census metropolitan areas, but close to them, are also growing faster than rural areas much farther away, so that's also a sign of an urban spread phenomenon.'' Canada's rural population is aging at a much faster rate than those in the urban centres, which tend to attract younger families, said Michael Haan, a sociology professor at Western University in London, Ont. "Demographers call cities population sinks for a reason,'' Haan said. "Imagine you had all sorts of water on a counter and it all just runs into the sink and it never comes out again.'' How to keep those sinks from overflowing has become an increasing concern for urban planners. "How do you create more density and a different built form that can help people age in place in the community they're in right now so that they don't feel they have to move somewhere else?" It's why suburban lots over the years have become smaller, circuitous streets designed for cars are being replaced with a transit-and-foot-friendly grid system, and dwellings are increasingly being designed to allow young families to age in place. "If we have a whole bunch of really young population, now we know that they're going to start to age in our communities,'' said Eleanor Mohammed, president of the Canadian Institute of Planners, and chief planner in Beaumont, Alta., which grew at a rate of 31 per cent between 2011 and 2016. "So, if your community is really suburban, how do you create more density and a different built form that can help people age in place in the community they're in right now so that they don't feel they have to move somewhere else?''