Home prices fell for the 25th consecutive month in August. Prices in 10 major markets dropped by a record 17.7% year over year. This was according to the S&P Case-Shiller Home Price 10-city index where a dropped 1.1% for the month from July.

The 20-city index recorded a record year-over-year decline of 16.6% with a 1% fall in August from July.

The Commerce Department reported on Tuesday that the number of vacant homes for sale held steady at about 2.8% in the third quarter. That's 65% higher than the long-term historic rate of 1.7%, and represents an excess inventory of nearly a million homes.

This number is homes for sales is important home price trends as owners of vacant properties especially the foreclosed ones would drop their prices to move out their inventory. This further push prices down.

The Case-Shiller indices compare the sale prices of the same homes yearly to establish the price trends. The price indices are considered one of the most accurate home price gauges.

The hardest hit of all 20 cities covered on an annual basis was Phoenix, where prices plunged 30.7% during the past 12 months. Las Vegas and Miami prices dropped 30.6% and 28.1% respectively.

None of the cities covered by in the report showed a price gain during the last 12 months. The cities that experienced the least declines were Dallas with just 2.7%, Charlotte NC, 2.8% and Boston, 4.7%.

In August from July, San Francisco saw the biggest price drops, with 3.5%. Phoenix and Las Vegas also reported a fall for the month with 2.9% and 2.4% respectively. Two cities showed gains in August; Cleveland prices up by 1.1% while Boston prices edged up 0.1%.