Most likely to pop? The ten most volatile housing markets in the United States Rank  Metropolitan area  One-year price rise (Through June 30)  1  San Luis Obispo, CA  20 percent  2  New Bedford, MA  17 percent  3  Ventura, CA  21 percent  4  Barnstable -Yarmouth, MA  15 percent  5  Santa Rosa, CA  13 percent  6  Orange County, CA  22 percent  7  Riverside, CA  25 percent  8  Los Angeles, CA  22 percent  9  Yuba City, CA  20 percent  10  Fort Pierce, FL  22 percent   Source:  Standard & Poor's

NEW YORK (CNN/Money) - Real estate: If it is a bubble, and it bursts, how at risk are you?

Like almost everything else in real estate, it depends on your location, according to a report from information provider Standard & Poor's. S&P has developed a housing volatility index (HVI) that attempts to identify which of the 331 U.S. metropolitan statistical areas (MSAs) are most vulnerable to housing price losses during an economic downturn.

The HVI examines historical records of housing prices, as reported by the Office of Federal Housing Enterprise Oversight, and focuses on the variabilty of those prices over the years.

One of the developers of the index, Francis Parisi, says that it reflects not just how much homes in those markets have gone up in price during the good years, but how much they have gone down during the bad. The steeper the price rises and price descents, the more vulnerable.

The index ignores other economic factors, such as consumer debt or mortgage rates.

S&P went as far back as the 1970s to examine the data for each market, according to Parisi. He stresses that S&P is not predicting a bubble burst nor is it saying that there will be an economic decline.

Some of the most volatile markets have enjoyed remarkable price run-ups recently.

Riverside, California, for example, which is the seventh most volatile real estate market according to the index, saw house prices balloon 25 percent from June 2003 through June 2004. Orange County California, No. 6, had gains of almost 22 percent over the same period.

Others on the index enjoyed more modest gains. Barnstable-Yarmouth, on Cape Cod, which the index judged to have the fifth highest probability of decline during a downturn, gained 15 percent this year.

The index's most volatile housing market is the San Luis Obispo area of Southern California and includes the towns of Atacascadero and Paso Robles. Other top Sun Belt finishers include Los Angeles, Fort Pierce, Florida, and Miami.

Northern locations scoring in the top twenty for volatility are Providence, Rhode Island, Long Island, New York, and Jersey City, New Jersey.

Locales that could expect to suffer the least during an economic downturn include Austin, Texas, which the HVI judged as the market with the lowest probability of market value decline, Provo, Utah (third) and Fort Wayne, Indiana (fourth). Many of the least volatile markets, however, had price run-ups of less than 2 percent during the last year. Tough to get rich on real estate at that rate.

The report points out that the highest house values are on the coasts with California and the Northeast, and that these tend to be among the most volatile. But homeowners tempted to cash in their gains and move to a lower cost area might want to consider carefully; the index indicates that many of those same areas will also provide the best opportunity for growth.