The proportion of million-dollar detached homes in Vancouver jumped from just 11 per cent a decade ago to more than 90 per cent last year – a dramatic increase that experts warn is "irrational" and could soon come to an end.

The decade-long price surge has transformed the city from one in which a house worth more than $1-million was once a rare luxury to a place where that million-dollar threshold – a psychological barrier that was once meticulously tracked – is now considered at the low end of the market. And it's a reality that financial experts and even the Bank of Canada have said is unsustainable.

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Researcher Andy Yan, acting director of Simon Fraser University's city program, released new data on Tuesday chronicling the prolonged increases in Vancouver since 2005, when the city was already by far the most expensive in Canada.

"The idea of a million-dollar house was a relative rarity a decade ago in Vancouver," he said.

While 11 per cent of detached houses within city limits were assessed at $1-million or higher in July, 2005, that figure was 91 per cent in July, 2015, said Mr. Yan, who examined 66,825 properties valued by BC Assessment.

Newly assessed values for this month will be sent out to homeowners in early 2017. Industry observers say the small number of detached homes listed earlier this year for less than $1-million in Vancouver tended to be on busy streets or tiny lots, or were tear-downs.

Phil Soper, chief executive officer of real estate firm Royal LePage, said the incredible price surges in Vancouver are unsustainable.

"You have severe affordability issues in Vancouver. It has become a serious public-policy issue, so it's not healthy," he said in an interview. "We've got a market in Vancouver that is appreciating too quickly. Prices are moving upward at an irrational rate."

The real estate map for Vancouver is divided into the west side and east side. There was once only a smattering of million-dollar properties east of the dividing line of Ontario Street. Today, the east side is awash with detached houses worth at least $1-million.

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Over the past 12 months, prices for detached homes in Vancouver have soared 38 per cent on the city's west side and climbed 36 per cent on the east side. The real estate craze has spread to the suburbs, where it is common to see price jumps of at least 35 per cent for detached properties since mid-2015.

David Ley, a professor of urban geography at the University of British Columbia, predicts prices will soften, not crash.

"No boom goes on forever," he said. "There are downturns, and we are certainly due for one here – not a hard landing but a softening of the current market."

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Prof. Ley said modest annual increases or even slight declines are possible. "My guess would be somewhere in the range of plus 5 per cent to minus 5 per cent," he said.

Vancouver's housing market rebounded after the 2008-09 recession and has been on a tear over the past three years. Prices for condos and townhouses across the region have rallied at least 25 per cent over the past 12 months.

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Mr. Soper and Mr. Yan said low interest rates, limited housing supply and foreign capital are among the key ingredients behind Vancouver's housing bonanza. Prof. Ley agrees that there are several important drivers, though he argues that buyers from China are the "decisive factor" in sales of high-end properties on Vancouver's west side, sending a ripple effect across the region.

Royal LePage produces a "price composite" in a formula that focuses on typical properties and excludes sales of luxury mansions. It said its sampling provides a better barometer of trends than average prices, which are skewed upward by sales of high-end properties.

The company's two-storey price composite for the city of Vancouver ascended to $2.36-million in the second quarter, up 30.7 per cent from the same period last year. The city of Toronto saw a 10.5-per-cent increase to $974,937.

The typical two-storey price is up 26.5 per cent over the past year to $1.45-million in the Vancouver region, compared with an 11.4-per-cent gain to $770,676 in the Toronto area.

Nationally, in 53 markets measured, Royal LePage's two-storey price composite improved to $619,671 in the second quarter, up 10.7 per cent from a year earlier. The firm's price for all housing types climbed 9.2 per cent over the past year to $520,223.