There's an unusual decline in housing inventory that's preventing home prices from falling further

• New listings of homes for sale are down more than 20% nationwide, according to Redfin. 
• "The lack of new listings is driving an unseasonal decline in the total number of homes for sale."
• Nearly half of homes on the market sell within two weeks, the highest portion in almost a year.

The housing market is facing an unusual lack of inventory that's keeping prices from falling further, according to real estate tracker Redfin.