First, your numbers are incorrect: https://beta.theglobeandmail.com/real-estate/bcs-foreign-buy...

10-14% of buyers SELF REPORTED as foreign, across METRO VANCOUVER, not some fancy neighbourhoods. That's the base minimum possible percentage of foreign buyers.

Then the 15% tax was introduced and dropped foreign purchases down to to 3-4%. Do you really think the ~8% stopped buying? No, they just used one of the trivially available loopholes like sending in their astronaut family or buying through a trust company. And many buyers were doing that even before the tax was introduced.