The folks behind the all-important Case-Shiller Home Price Index have released their numbers for March 2011 and for the eighth month in a row, the average price of a home in the U.S. has declined. Only two of the 20 cities in the index — Seattle and Washington, D.C. — experienced even a slight uptick from the previous month, while a dozen cities are at or near four-year low points.

Among those cities that are experience new lows are Atlanta, Chicago, Cleveland, Miami, Minneapolis, New York, and Tampa.

The hardest hit cities continue to be Detroit, which has the lowest index value of all 20 areas on the list, Las Vegas, and Phoenix, both of which have indices that are less than half of what they were during the mid-decade real estate boom.

Meanwhile, Washingtons on both coasts have something to brag about. Both Seattle and D.C. experienced slight bumps in their index values.

You can see the whole spreadsheet here.

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