Home prices continued their post-tax-credit swoon in October, according to the S&P/Case-Shiller Home Price Indices released Tuesday.

The 10-City Composite Index was up only 0.2% and the 20-City Composite fell 0.8% from their levels in October 2009, with the former down 1.2% sequentially and the latter down 1.3%. Prices decreased in all 20 MSAs from September, and only four markets -- Los Angeles, San Diego, San Francisco and Washington DC -- showed year-over-year gains.

Moreover, six markets -- Atlanta, Charlotte, Miami, Portland, Seattle and Tampa -- hit their lowest levels since home prices started to fall in 2006 and 2007, meaning that average home prices in those markets have fallen beyond the recent lows seen in most other markets in the spring of 2009.

David Blitzer, chairman of the index committee at S&P, sounded morose in his prepared statement. "The double-dip is almost here, as six cities set new lows for the period since the 2006 peaks. There is no good news in October¹s report ... The trends we have seen over the past few months have not changed. The tax incentives are over and the national economy remained lackluster in October."

He continued, "Existing homes sales and housing starts have been reported for both October and November, and neither is giving any sense of optimism ... sales are down more than 25% and the months' supply of unsold homes is about 50% above where it was during the same months of last year. Housing starts are still hovering near 30-year lows. While delinquency rates might have seen some recent improvement, it is only on a relative basis. They are still well above their historic averages, in both the prime and sub-prime markets."

Detroit remained the nation's worst housing market in terms of price appreciation, having fallen to an index of 68.86, meaning that the price of the average home sold in October in the market was less than 69% of what it would have sold for in January of 2000. Las Vegas is nearly back to January 2000 price-wise with an index of 100.97. Cleveland (102.20), Atlanta (103.30), and Phoenix (105.97) were not far behind.

Chicago led the nation in year-over-year losses with a decline of 6.5% (2% from September alone). Atlanta followed closely with a 6.2% year-over-year drop and a 2.9% month-to-month plunge. Detroit dove 5.5% under October 2009 and 2.5% below September this year. Portland and Seattle were down 5.2% and 4.1%, respectively, year-over-year and down 1.5% and 1.3% sequentially.

Washington, up 3.7% year-over-year but down 0.2% from September, continued as the nation's strongest market with an index of 186.67. Los Angeles was next at 174.05, up 3.3% but down 0.7% respectively. New York was next at 171.50, down 1.7% and 1.6%, followed by San Diego at 159.99, up 3% but down 1.5%, and Boston at 154.35, down 0.2% and 1.2%.

The news sent shares in the entire public home builder sector down in early-session trading Tuesday.