July home prices dropped 16.3% after a year, according to the Standard & Poor's/Case-Shiller Report released last September 30. This was the sharpest so far since the start of the index in 2000.

The Standard & Poor's/Case-Shiller 20-city housing index sunk a record 16.3% in July from the same month last year while the 10-city index dropped 17.5%, the biggest decline in its 21-year history.

Prices in the 20-city index have plunged nearly 20% since July 2006 when the index was at its peak while. the 10-city index has decreased more than 21% since its peak in June 2006.

No city in the Case-Shiller 20-city index experienced price gains in July compared to a year, the fourth straight month that this has happened.

Las Vegas prices dropped the most at nearly 30 percent, Phoenix plunging 29 percent and Miami, 28 percent. Prices in the seven cities in the Sunbelt all went down between 20 percent and 30 percent from a year ago.

Seven cities showed positive or flat returns from June to July, down from nine that showed month-over-month gains in June. Atlanta, Boston, Dallas, Denver and Minneapolis showed positive results for three months or more.