Tampa area home prices are down 20.9 percent for the year and 32.4 percent since the July 2006 peak, according to the latest calculations from the S&P/Case-Shiller home price index.

Why are Case-Shiller's price plunges so different from those published by Florida Realtors yesterday? Simple. Case-Shiller tracks repeat sales of individual homes, so you always get apples-to-apples comparisons.

Realtors showed a 27 percent annual price decline and a 39 percent decline from the June 2006 peak. But since people are buying smaller homes - leading to many apples-to-oranges comparisons - Realtor statistics tend to exaggerate the dip in home values.

One stipulation: Case-Shiller lags a month behind the Realtor index. It's publishing November numbers while Realtors have already closed out 2008.

Tampa was the 7th most impacted by annual price declines in Case-Shiller's 20-city index:

Phoenix: -32.9 percent

Las Vegas: -31.6 percent

San Francisco: -30.8 percent

Miami: -28.7 percent

Los Angeles: -26.9 percent

San Diego: -25.8 percent

Tampa: -20.9 percent

Quite a massacre in the Sun Belt, eh? Note that Dallas and Atlanta are doing much better, Dallas because of oil and Atlanta because prices never shot up as high during the housing boom.