Median existing-home prices declined in the second quarter, with 27% of metropolitan statistical areas (MSAs) experiencing price gains from a year ago, according to data released by the National Association of Realtors (NAR).

The median existing single-family home price rose in 41 out of 151 MSAs in the second quarter of this year from the same period in 2010, including four with double-digit increases; one MSA remained unchanged; and 109 areas showed price declines. In the first quarter, 34 metro areas posted gains from a year earlier.

NAR's Housing Affordability Index stood at 176.6 in the second quarter - the third highest on record after the first quarter of 2011 and fourth quarter of 2010. The index measures the relationship between median home price, median family income and mortgage interest rates; the higher the index, the greater household purchasing power.

The national median existing single-family home price was $171,900 in the second quarter - down 2.8% from $176,800 in the second quarter of 2010. Distressed homes, typically sold at a discount of about 20%, accounted for 33% of second quarter sales - down from 39% in the first quarter and up slightly from the 32% level a year earlier.

However, total state existing-home sales, including single-family and condo, declined 5.4% to a seasonally adjusted annual rate of 4.86 million in the second quarter - down from 5.14 million in the first quarter, and 12.7% below a 5.57 million pace during the second quarter of 2010 (which also saw the closing deadline for the federal home-buyer tax credit).