Home prices in the U.S. were 0.6 percent lower in the second quarter than in the first quarter of 2011, according to the Federal Housing Finance Agency (FHFA).

The agency’s index is calculated using purchase price information on homes backing mortgages that have been sold to or guaranteed by Fannie Mae and Freddie Mac.

Looking at this data over the past year, home prices have fallen 5.9 percent. That’s the biggest annual drop recorded by the federal agency since the second quarter of 2009. As of June, FHFA says its index indicates home prices are down 18.8 percent from their April 2007 peak.

FHFA’s ‘all-transactions’ index, which includes data from mortgages used for both home purchases and refinancings,

decreased 1.9 percent in the latest quarter and is down 4.5 percent over the four-quarter period.

While the national, purchase-only house price index fell 5.9 percent from the second quarter of 2010 to the second quarter of 2011, FHFA says prices of other goods and services rose 4.5 percent over the same period.

Accordingly, the inflation-adjusted price of homes represents a decline of approximately 10.0 percent over the last year.

FHFA’s purchase-only price gauge declined from the first to the second quarter in 31 states.

Quarter-over-quarter, prices held up best in the District of Columbia (+7.15%), Hawaii (+5.53%), and Oklahoma (+4.10%).

Looking at the change in purchase prices over the previous year, only the District of Columbia (+12.13%), North Dakota (+3.87%), and Oklahoma (+0.28%) were in positive territory.

At the local level, price appreciation over the 12-month period ending in June was greatest in Pittsburgh, Pennsylvania (+3.69%) – the only one of the 25 most populated metropolitan areas in the plus column.

Annual price declines were greatest in the Atlanta, Georgia (-14.09%) metro area.