New York City’s housing market was already struggling with a historic mismatch involving a flood of luxury inventory and a shortage of buyers looking for housing in that price-range (instead, the city has continued to suffer from a shortage of housing affordable to its workforce), when the city adopted a new transfer tax on properties valued over $2 million.
https://www.zerohedge.com/markets/manhattan-home-prices-down-8-q3-largest-slump-2011