The price of homes in a dozen U.S. markets have reached their lowest level since the housing bubble burst in 2006, according to the Standard & Poor's/Case-Shiller home-price index released Tuesday.

The 12 cities now at their lowest levels include Atlanta, Charlotte, Chicago, Cleveland, Detroit, Las Vegas, Miami, Minneapolis, New York, Phoenix, Portland, Ore., and Tampa.

The drop has been attributed to foreclosures, a glut of unsold homes, and the reluctance or inability of many to buy homes that have have depressed values.

The report also showed that nationwide, home prices fell for the eighth straight month -- reaching pre-2002 levels.
  
Most economists think prices nationally will drop at least another 5 percent by the end of the year.

"There are not many people with the money or the ability to borrow to buy a house," Daniel Martin, an economist with the Economist Intelligence Unit, told ABC News.

"What we have is very weak demand, a heck of a lot of supply," he added.  "And that probably means house prices will continue falling."