By Nick Timiraos

See inventory and prices in major markets.

The number of homes listed for sale, which stood at an 11-year low at the end of last year, fell even further in January, according to a report released Thursday.

There were just 1.48 million homes listed for sale at the end of January, down by 5.6% from December and by 16.5% from one year ago, according to data compiled by Realtor.com. That’s the lowest level since the firm began its count in 2007. The National Association of Realtors separately reported last month that inventory ended 2012 at an 11-year low.

It’s normal for inventories to decline in December and January, as home sellers wait for the start of the spring buying season to list their homes for sale. But the shortage of homes for sale in a growing number of U.S. markets is maddening for would-be buyers who frequently complain that there aren’t enough good choices. Bidding wars are becoming more common.

Of the 30 largest U.S. markets, only Miami saw inventories increase in January from December, though they were still 10% below last year’s level. Other cities that have witnessed huge drops over the past year saw more modest monthly declines: inventories fell by less than 2% in Orlando, Phoenix, Atlanta, and Fort Lauderdale, Fla.

Several others reported huge monthly declines. There were just 1,800 homes listed in San Francisco, down by 21% from December and by 47% from one year ago. There were fewer than 4,000 homes listed in Seattle, down by 9% from December. Last year at this time, there were 7,175 listed for sale, and two years ago, there were more than 11,000.

Seattle and San Francisco have witnessed some of the sharpest price increases over the past year; median asking prices were up by 16.4% and 23.7% in both cities, respectively. Nationally, median asking prices were down by 0.5% from December and up by 0.8% from one year ago.

Housing inventory is low right now for several reasons. Notably, housing demand has picked up over the past 18 months, first as investors moved in to snatch up bargains on distressed properties, and later as demand from traditional buyers has picked up. Many investors have been buying homes that can be held as rental properties, which has kept them off the market.

Meanwhile, banks have slowed down their pace of foreclosure. The share of delinquent mortgages has been declining over the past three years, though it is still high. Lenders and other mortgage companies are also facing new processing requirements for foreclosures in some states, such as California, that have led to further declines in foreclosed-property listings.

A separate report Thursday from RealtyTrac, a real-estate firm, said that newly initiated foreclosures dropped by 11% in January and stood 28% below last year’s levels to a 6½ year low. A large part of that decline was due to the new “homeowner bill of rights” that took effect in California.

Many homeowners may be unwilling or unable to list their homes for sale because they don’t have any equity, or because they don’t have enough equity to sell their home and make a down payment their next home. Others that have equity may simply be unwilling to sell at a steep discount to prices that they would have paid in 2005, 2006 or 2007.

The Realtor.com figures include sale listings from more than 900 multiple-listing services across the country. They don’t cover all homes for sale, including those that are “for sale by owner” and newly constructed homes that aren’t always listed by the services.

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