Urban planner Andy Yan is fascinated by housing supply and demand in Vancouver, and he believes both are factors in the city's affordability crisis.

The number of residences in Vancouver categorized as occupied single-detached houses has dropped 14.5 per cent over the past decade as the crisis deepens, said Mr. Yan, director of Simon Fraser University's City Program.

Developers are touting increased supply as the solution while some housing critics say tightening rules on foreign purchasers should be the top priority, but Mr. Yan said the complex problems don't stem from solely supply or demand.

The shrinking supply of detached homes has combined with other factors such as foreign buyers, speculation and low interest rates to result in higher prices for the remaining detached properties, he said. There has been a ripple effect into the multifamily market, with prices climbing too for condos and townhomes.

"This raises issues about how to achieve a level of co-operation in terms of regional action on housing, and different views on what constitutes a home," said Mr. Yan, who conducted an analysis based on Statistics Canada's dwelling data from census numbers in 2006 and 2016.

Within Vancouver's city limits last year, there were 41,330 detached properties in which a person or persons resided in the private dwelling, down from 48,365 in 2006, according to Statscan.

While the number of detached homes has dropped, condos and townhouses have proliferated. The total number of Vancouver dwellings of various types has climbed 12.1 per cent over the past decade to 283,915.

The affordability crisis is a thorny problem for policy makers to tackle. "The single-detached house may be dying out in most municipalities simply because of economics," said Mr. Yan, who noted that there has been an increase in multifamily units.

In the Vancouver region, including far-flung suburbs, detached homes are in the minority among occupied private dwellings in 13 of 22 markets.

The region remains expensive, despite a 15-per-cent tax imposed by the British Columbia government last August on foreign home buyers in the area – a measure designed to cool off the real estate market.

"The supply of detached houses has been declining, but what you have increasingly seen over the years is one suite or two suites inside those houses, effectively making them duplexes or triplexes," Mr. Yan said.

He pointed out that many detached houses have been demolished along major roads to clear the way for multifamily units such as condos and townhomes.

In 2006, single-detached houses accounted for 19.1 per cent of the total number of occupied private dwellings in Vancouver. Last year, that proportion fell to 14.6 per cent.

On the University Endowment Lands at the University of British Columbia, only 7 per cent of the total number of occupied private dwellings are detached houses – the lowest proportion last year among the 22 markets studied by Mr. Yan.

Besides the University Endowment Lands, detached properties accounted for less than half the total number of dwelling types last year in a dozen other communities: City of North Vancouver (12 per cent); New Westminster (15 per cent); Vancouver (15 per cent); Burnaby (21 per cent); City of Langley (23 per cent); White Rock (25 per cent); Port Moody (30 per cent); Richmond (33 per cent); Surrey (35 per cent); Port Coquitlam (38 per cent); Coquitlam (39 per cent); and Pitt Meadows (43 per cent).

Detached houses still play leading roles in nine municipalities, making it complicated to develop a cohesive strategy to make housing less expensive in the region, Mr. Yan said.

For Metro Vancouver as a whole, detached properties accounted for 29 per cent of the total number of occupied private dwelling types last year while multifamily units such as condos and townhomes made up the majority.

In Lions Bay, detached properties accounted for 95 per cent of the total number of the occupied private dwelling types last year in the small community. Lions Bay has the highest proportion of detached houses among markets in the Vancouver area.

Besides Lions Bay, detached properties accounted for more than half the total number of dwellings in the following municipalities: Bowen Island (89 per cent); Belcarra (82 per cent); Anmore (70 per cent); Delta (59 per cent); Maple Ridge (56 per cent); West Vancouver (55 per cent); District of North Vancouver (52 per cent); and Township of Langley (52 per cent).

Affordability remains a major challenge, Vancouver City Savings Credit Union said in a recent report.

The median price of detached houses sold in the B.C. Lower Mainland reached $988,000 for the 12 months ended Feb. 28, up 17.6 per cent from the year-earlier period, said Vancity, which examined an area that is slightly larger than what Mr. Yan studied.

Median prices vary widely, with detached properties in the 12 months ended Feb. 28 fetching $700,000 in Maple Ridge and $3.24-million in West Vancouver, said Vancity's report, based on data from land title registrations supplied by Landcor Data Corp.

Vancity said there are "pockets of affordability" in the suburbs, despite the runup in prices. The median price for condo transactions during the 12 months ended on Feb. 28 in the City of Langley was $225,000, or a 15.4-per-cent gain over the previous one-year period.