It looks like the nation's last hold-out -- the last bastion of the housing bubble, if you will -- has finally started to burst. Or at least deflate.

Manhattan, which remains, despite the nation's decade of policy errors, the capital of the world, registered its fourth straight quarterly decline in apartment sales in Q4 2008, according to research compiled by Prudential Douglas Elliman Real Estate (pdf).

Transactions in Q4 2008 fell 9.4% from a year ago to 2,282, Prudential said. Further, while the median price of all units (new and existing) rose 5.9% to $900,000, the median price for re-sale properties fell 3.6% to $732,500. Luxury unit prices fell 3.9% to $4.13 million

Just as telling: inventories have soared. Listings increased 39.3% to 9,081 units compared to a year ago, with the average days a listing was on the market before sale rising to 159 days, from 131 days a year ago.

Driven by record investment banking / financial sector salaries and bonuses, and by creative mortgage forms, New York City's real estate market, specifically the borough of Manhattan, experienced "a 5-year period of clearly unsustainable price gains," so says economist Peter Dawson. Manhattan, he says, was able to hold on in 2007 as the housing slump devastated prices in the U.S., particularly in the California, Southwest U.S., and Florida markets, but the financial crisis that depleted New York's investment banking employee ranks is finally showing up in Manhattan's residential real estate market, he said.