NEW YORK -- Prices of single-family homes plunged a record 16.3 percent in July from a year earlier, extending declines that have plagued the housing market for two years, according to the Standard & Poor's/Case-Shiller Home Price Indexes.

The S&P/Case Shiller composite index of 20 metropolitan areas fell 0.9 percent in July from June, S&P said in a statement on Tuesday. Since the peak of the housing boom in July 2006, the index has dropped 19.5 percent, it said.

S&P said its composite index of 10 metropolitan areas declined 1.1 percent in July for a 17.5 percent year-over-year drop. From two years ago, the index is down 21.1 percent.

The pace of home price declines has slowed in the past three months, however, S&P said.