That's a very good question.
Canada Mortgage and Housing Corporation has not done any studies on other OECD nations. So my answer can only cover Canada.
In Canada, a number of factors have caused demand to go up: low interest rates, population growth and income growth. On the one hand, all these factors have resulted in strong growth in demand for housing in Canada. On the other hand, supply has not kept up. In some places, like Toronto and Vancouver, we've seen a long-term trend of supply not keeping pace with demand. In those cities, we have also seen fairly strong growth in house prices over a long period.
In the rest of Canada, it's a more recent phenomenon. During the pandemic, many people left the cities for the suburbs and rural areas. This led to a very sudden increase in supply. The increase in house prices spread from Vancouver and Toronto to other major urban centres.