An historic volume of foreclosures and short sales have dramatically impacted the supply of an already high level of inventory of unsold existing homes and continue to drive down prices. Credit standards have moved from the loosest requirements in history to some of the toughest, with many lenders now requiring 25 to 30 percent down payments due to the distressed nature of the market. 
Factors negatively influencing housing prices:

There are however some positive signs in the housing market;