S&P/Case-Shiller national home price index falls again

In the first quarter of 2012, the S&P/Case-Shiller national home price index fell 1.9% year-over-year:

Data through March 2012, released today by S&P Indices for its S&P/Case-Shiller Home Price Indices, the leading measure of U.S. home prices, showed that all three headline composites ended the first quarter of 2012 at new post-crisis lows. The national composite fell by 2.0% in the first quarter of 2012 and was down 1.9% versus the first quarter of 2011. The 10- and 20-City Composites posted respective annual returns of -2.8% and -2.6% in March 2012. Month-over-month, their changes were minimal; average home prices in the 10-City Composite fell by 0.1% compared to February and the 20-City remained basically unchanged in March over February. However, with these latest data, all three composites still posted their lowest levels since the housing crisis began in mid-2006. ...

The S&P/Case-Shiller U.S. National Home Price Index, which covers all nine U.S. census divisions, posted a 1.9% decline in the first quarter of 2012 over the first quarter of 2011.

Unfortunately, crappy journalists at several different news organizations keep emphasizing the 20-city numbers instead of the national numbers. Why? Why would anyone think that an index that measures a random selection of 20 cities deserves more emphasis than an index that covers the overall country? (Note: The S&P/Case-Shiller national home price index really only measures 70% of the country, but that's still way more than just 20 cities.)