NEW YORK (CNNMoney.com) -- Residential real estate has posted another record decline.

The S&P Case/Shiller Home Price index of 20 key markets, released Tuesday, shows that home prices plunged 10.7% in the 12 months ending January. That marks their lowest level since the index launched in 2000.

Of those 20 metro areas, 16 reported record annual declines. Ten of those cities posted double digit declines through the 12 months that ended in January.

The survey's 10-city index fell 11.4% year-over-year, its steepest decline since its inception in 1987.

A national decline. While regional declines in home prices are not uncommon, the current decline is the "first national decline we've had," said Robert Shiller, Yale professor of economics and co-founder of the index.

"In a historical context we're down substantially, down more than at any other time that we've been keeping track," he added.

Las Vegas and Miami reported the weakest markets in January, with each city posting an annual decline of 19.3%. Phoenix was the second worst with a decline of 18.2%.

Washington and Minneapolis also registered double digit declines in January.

Only one city, Charlotte N.C., posted a modest price increase of 1.8%.

"Unfortunately it does not look like early 2008 is marking any turnaround in the housing market," says David M. Blitzer, Chairman of the Index Committee at Standard & Poor's.

Housing glut. Michael Strauss, chief economist at investment firm Commonfund, says that steep price declines are no surprise, given the number of homes on the market.

"When inventory is so high we're likely to see a decline in prices," he said.

Cities like Las Vegas and Miami, where speculative buyers helped fuel the housing boom, are seeing sharp reversals.

"Some of the cities that soared the most are now retracting the most," according to Strauss. "Though it may be disappointing to some, from an economic stand point it makes a lot of sense."

Silver lining. The Case/Shiller data comes one day after a report from the National Association of Realtors that showed a modest increase in sales of existing single-family homes in January, thanks to the plunge in prices.

Mike Schenk, senior economist for the Credit Union National Association, says the decline in home prices is a symptom of serious economic problems, but adds that the environment is improving for home buyers.

"Affordability is actually quite high," he said. "This is a pretty good market to consider taking the plunge. And it's going to get better as we go forward."

Subprime fallout. Across the nation, the market for lower-priced homes has been the most volatile over the last 12 months, a phenomenon Shiller thinks is a result of the ongoing subprime crisis.

"It's going to take those markets a long time to recover," Shiller said.

And the housing crisis, in turn, has rocked Wall Street.

The Case/Shiller indexes compare the sale prices of the exact same homes. The industry considers this survey to be among the most accurate snapshots of housing prices.