A house next door to me sat vacant for 4 years here in Vancouver. The owner couldn't sell at the asking price. The owner never lived in the house himself ever. He couldn't lower the price because then he would be losing money (selling it for less than what he bought it for).

Over that 4 year period, immigration to Canada dropped dramatically.

It just recently sold for slightly lower than the asking price (but slightly more than what the owner had bought it for 4 years prior). It was sold to a new immigrant to Canada. At least the new owner is actually living in it.

Why would developers want to build so much supply that the price drops?