Vancouver's real estate market has often been compared to various markets in California, including Los Angeles, San Diego and San Francisco.
UPDATE (thanks jmk for the stats tips):
I am now showing analysis using the Case Shiller Price Index and the UBC CUER Data based on annual price change calculations. The correlation between Vancouver and Los Angeles is 0.40; San Francisco is 0.22; San Diego is 0.29; Composite is 0.20; and Calgary is 0.38. I also did correlation analysis for Portland and Seattle. Portland is 0.22 with Vancouver. Surprisingly Seattle is has a correlation coefficient of only 0.0559 with Vancouver.
I found historical median price data for San Francisco, Los Angeles and San Diego and here is the comparison between Vancouver and those markets. I have adjusted Vancouver's prices for the difference between the US and CDN currencies based on historical exchange rates in the year in question.