Buyers and investors beware: the number of real-estate markets that are now overvalued is growing rapidly.

Of the top 100 real-estate markets in the U.S., 14 are now overvalued -- more than double the number that were at the end of the first quarter in 2015, according to a report released on Monday by real estate analytics firm CoreLogic, which examines market data for the first half of 2015. An overvalued housing market has home prices that are 10% or more above the long-term sustainable level (which measures home affordability based on the per capita income levels in the area).

The primary driver behind the overvaluation of more housing markets is supply, says Sam Khatar, the chief economist at CoreLogic. “Builders are not building enough -- they’ve focused on margins and not scale,” he says. This, in turn, has led them to focus on the upper end at the expense of the middle and lower end of the markets, where demand is strong once again, he says.

The most overvalued housing market in the U.S.

Plus, this all comes at a time when home prices are rising rapidly, even as incomes aren’t seeing as much growth. In the past two years, home prices in the U.S. have climbed 11.5% to a median price of $189,500, according to data from real-estate firm RealtyTrac. And in some markets, home price appreciation has climbed more than 20%. Incomes, meanwhile, have not kept pace: Real disposable personal income in the U.S. has increased only about 5.5% over the past two years, according to data from the Federal Reserve Bank of St. Louis using inflation-adjusted numbers.

Of course, there are still plenty of individual deals to be found, even in overvalued markets. And, as Khatar points out, “just because a market is overvalued doesn’t mean it’s a bubble.”

Here are the 10 most overvalued housing markets in America, according to CoreLogic.

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Austin, Texas

The rapidly growing Austin and Round Rock area lands in the No. 1 spot on this list with home prices a staggering 42.3% over what’s considered sustainable. Since January 2014, home prices have risen 16.3%, compared with 10.4% in 2013.

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Houston

Like in Austin, home prices in the Houston area, which includes The Woodlands and Sugar Land, have risen more than 16% since early 2014 — and this oil capital also now has a problem with overvaluation. Home prices are now 25.4% over what’s considered sustainable.

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Charleston, S.C.

Homes in historic Charleston and North Charleston are priced at 23.4% more than what’s sustainable and have grown in value 12.8% since January 2014 (as compared with 5.4% in 2013).

Construction cranes dot the Miami, Florida skyline, shown, Sunday, March 11, 2007.(Photographer: Richard Sheinwald/ Bloomberg News) Bloomberg

Miami

Hit hard by the recession, Miami is back -- and then some. Homes here (the area includes Miami, Miami Beach and Kendall) are now priced, on average, 20.6% more than what’s sustainable. Meanwhile, home prices continue to appreciate rapidly (15.6% since January 2014 compared with 11.5% in 2013).

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Washington, D.C.

Though a vibrant place to live, the D.C. area has its downsides, including the worst traffic in the nation and pricey real estate that most cannot afford. Homes here (the area includes Arlington and Alexandria, Va.) are priced at more than 19% over sustainable levels.

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Knoxville, Tenn.

Knoxville is one of two spots in Tennessee that make this list, with homes now priced at 14.4% over sustainable levels. Home prices have appreciated 11.3% since January 2014, compared with 4.5% in 2013.

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Philadelphia

Home prices have ascended rapidly in the Philly area (up 16.7% since early 2014, which means it has the fastest home price appreciation of any town on this top-10 list), and now they are priced at 14.2% over sustainable levels.

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Dallas

Cities in Texas dominate this list (they make up four of the top 10) in large part because their robust economy and relative affordability have attracted many people to the area in recent years. However, the housing supply hasn’t been able to keep up with demand, explains Khatar. In the Dallas area, including Plano and Irving, homes are priced at 14% over sustainable levels.

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San Antonio

This is the fourth Texas city on this list; its home prices are valued at 12.4% over sustainable levels. Home price appreciation in the area (which includes New Braunfels) since early 2014 was 10.3%, compared with 6% in 2013.

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Nashville, Tenn.

Many cash-strapped residents in the Nashville area (which includes Davidson, Murfreesboro and Franklin) are likely singing a sad song about their housing market: Homes are now priced at 12.3% over what’s considered sustainable, after having grown 14.1% since early 2014.