I will let the pictures do the talking, fiscal reality meets physical realty. My opinions on why this is happening and how much farther it could go.
Price declines 10-18%, Sales Declines of $+6 billion, listing discounts increasing to greater than +10%, average days on the market increasing over 175 days, you get the picture and with Job losses increasing from 6-10% the median income catchment area is declining, so the justifiable value (median income/media value ratio) has even more pressure on it.
The neighborhood details are in the Prudential report, and remember the numbers may be goosed to be positive considering the source. Download Manhattan_10YR_2009