America's 10 Sickest Housing Markets (Slideshow)

For three years, the real estate market has been going in one direction -- primarily down. Some areas, however, have begun to recover. Recent S&P/Case-Shiller data show that among the top 20 housing markets in the U.S., 18 had very modest improvements in sales prices during May. Others, like Washington and Boston, have began to at least stabilize from a year ago.

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Few markets, however, can match Washington and Boston. Robert Shiller has been stating that home prices could fall another 10 percent in the next year. Inventories in some major metropolitan areas would then take years of sales to get back to 2005 levels. At that time, the normal inventory of homes for sale was replaced on average every six months and it was unusual for a house to be on the market for a year.

Foreclosure rates remain high and only the robo-signing scandal has slowed the process. Once this is resolved, economists fear that the market will be flooded with even more vacant, unsold homes.

24/7 Wall St. has taken a new look at the housing market to find the very weakest cities by identifying those with the highest homeowner vacancy rates and rental vacancy rates. These are markets where demand has clearly collapsed.