NEW YORK CITY-Home prices have tumbled for the sixth consecutive month despite high home affordability and low interest rates. The latest S&P/Case-Shiller indices showed declines for 16 of the 20 cities it ranks in February 2012, an indication that a slight uptick in sales hasn't materialized into normal-market pricing -- just yet.

Nine cities, including Atlanta, Charlotte, Chicago, Cleveland, Las Vegas, New York, Portland, Seattle and Tampa, and both S&P's 10- and 20- city composites, hit new post-crisis lows. Atlanta continued its downward spiral, posting its lowest annual rate of decline in the 20-year history of the index at -17.3%. S&P says the 10-city composite declined 3.6% and the 20-city was down 3.5% compared to February 2011, which is less than January's -4.1% and -3.9%, respectively.

David Blitzer, chairman of the index committee at S&P Indices, comments: "While there might be pieces of good news in this report, such as some improvement in many annual rates of return, February 2012 data confirm that, broadly-speaking, home prices continued to decline in the early months of the year."

According to S&P, the chart above depicts the annual returns of the 10-city and the 20-city composite home price indices. In February 2012, both composites fell by 0.8% over the month, resulting in annual returns of -3.6% and -3.5%, respectively.

Conversely, median home prices posted a slight gain in February, according to the National Association of Realtors, which measures home pricing and sales on a month-to-month basis. NAR says total existing-home sales slipped 0.9% to a seasonally adjusted annual rate of 4.59 million in February from an upwardly revised 4.63 million in January, but are 8.8% higher than the 4.22 million-unit level in February 2011.