A record number of real estate boom towns reads like the lyrics to a Johnny Cash ditty and that isn't music to the economy's ears.

"I've Been Everywhere" could be the name of a new Federal Deposit Insurance Corporation (FDIC) report on boom markets "Revisited U.S. Home Prices: Does Bust Always Follow Boom?"

The report says 15 percent of the 362 metropolitan areas in the "Office of Federal Housing Oversight's Home Price Index" are now boom towns.

By FDIC's definition, boom towns are those where inflation adjusted home prices increased at least 30 percent in the past three years.

The new number of boom towns represents the highest proportion of "boom" markets nationwide in the 30 years OFHEO has tracked home prices. There are now 55 boom markets, 72 percent more than the 22 markets just two years earlier and only nine boom markets in 2000.

The boom market boom continues to defy experts' predictions that cooler markets would prevail by now, but the report says the same conditions that are fueling the boom could cause it to go bust in a much bigger way than in the past.

The FDIC economists found that only 17 percent of local U.S. housing booms in the 1978-1998 period ended in busts, defined as a 15 percent or greater drop in nominal home prices over five years. In most regions, boom-ignited home price increases eventually taper off, flatten and stabilize for a time before taking off again. Typically the effect is felt locally as local economies independently go boom and bust.

With a record number of boom towns, however, report authors, FDIC economists Cynthia Angell and Norman Williams say more widespread boom factors may be in play and a different bust scenario could play out.

"The notable expansion in the number of boom markets in 2004 suggests that national factors could be helping to drive home prices higher. If national factors are coming more into play, then clearly the most important factors to look to would be the availability, price and terms of mortgage credit," the report says.

Along with mortgage rates rising, a big risk is also the increased use of more leverage to buy a home -- no -- and low-downpayment loans, adjustable rate mortgages (ARMs), interest-only loans and subprime mortgage lending. More speculative home buying, as revealed by the burgeoning second-home market, is also a risk factor, the report says.

"The broadening of the U.S. housing boom during 2004 may imply a growing role for national factors including the availability, price, and terms of mortgage credit in explaining home price trends. To the extent that credit conditions are in fact driving home price trends, the implication would be that a reversal in mortgage market conditions could contribute to an end of the housing boom. While history clearly shows that housing booms don't last forever, the manner in which they end matters for mortgage lenders and borrowers alike," the report said.

Most at risk are areas of Florida, New England, the Northeast, California and other Western States where boom towns are concentrated.

"While our analysis shows that boom does not necessarily lead to bust, it remains to be seen to what degree the current situation might differ from our previous experience in the U.S. housing market," the report said.