A huge number!
Ok this is New York, we are talking about. Manhattan to be precise, which as we know, is not as world class as Vancouver and has lots of land.
Actually the drop is probably much higher, as landlords are giving big incentives for leases, such as two months free rent for a 14 month lease. That is equivilent to another 10%+ drop!:
http://www.bloomberg.com/apps/news?pid=newsarchive&sid=a2UfZHjKxKrk
Of course this could never happen in Vancouver. BTW I tried looking up the Vancouver Vacancy rate, but had a hard time. Vacancy rates have increased across Canada with increased home ownership, by 1% according to the CMHC, but I couldn't find precise numbers for Olympicville.
