The asking prices of homes listed for sale continued to fall in January across most U.S. markets, while listed inventory continued to fall as well, according to a study released Monday morning by Altos Research and market analysis firm Real IQ. The Altoa 10-City Composite Price Index, which tracks single family homes in Boston, Chicago, New York, Los Angeles, San Diego, San Francisco, Miami, Las Vegas, Washington D.C, Denver, found that asking prices fell 2.1 percent in January versus December 2008. Home prices are down 2.4 percent during the most recent three-month period. Asking prices fell at the fastest rate in Las Vegas -- down 5.4 percent during January -- and 8.8 percent during the past three months. Sin City has posted the fastest rate of decline in asking prices in the nation for ten straight months, the firms said. And while listing prices rose at the fastest rate in Miami -- up 1.5 pecent in January -- the Altos/Real IQ report makes it clear that aggregate price increases in these markets are a function of a shift in the class of properties listed for sale moreso than an actual increase in the prices of individual properties. “Despite continuing decreases in inventory levels, asking prices remained on a steep downward path in January,” said Michael Simonsen, CEO and co-founder of Altos Research. “The trends appear to be continuing. We can find no signs of a turn-around in the data as of the first week of February.” Inventory levels declined in most major markets, with the exception of Portland, Seattle, Charlotte and Salt Lake City. Across the 10-City Composite Index markets, inventory declined by 3.3 percent in January, and 9.7 percent during the most recent three-month period. Inventory fell by more than 5 percent in Detroit, Boston, Atlanta and Cleveland during January. “Inventory levels generally increase in January as sellers anticipate the seasonally strong spring selling season,” said Stephen Bedikian, partner and research director for Real IQ. “So far we are seeing the opposite as inventory levels are continuing the decline they began in the summer of last year. The big test will come over the next few months as any increase in inventory will exacerbate the already large imbalance of housing supply and demand by adding to the existing overhang of available homes.” Suggesting that markets could ill afford an influx of new housing inventory, the median days-on-market rose in all markets during January, staying above 100 or more days-on-market in every major market, according to Altos and Real IQ. By far, the market with the slowest rate of inventory turnover was Miami, at a median of 189 days-on-market -- or more than six months. Miami has experienced the slowest market turnover in every month since September 2007, while Salt Lake City enjoyed the fastest rate of turnover with a median days-on-market of 101. For more information, visit http://www.altosresearch.com and http://www.realiq.com. Write to Paul Jackson at paul.jackson@housingwire.com.