The U.S. housing sector is gradually returning to pre-crisis levels. Home prices rose for four consecutive years to a median of $222,400 at the end of 2015, the highest since 2007. Prices rose further in the second quarter — by 4.9% from the same time a year ago. With increased home values as well as continued job and income growth there are plenty of reasons for optimism in the U.S. economy.

Not all U.S. housing markets, however, have returned to pre-crisis levels. According to data released in August by the National Association of Realtors, housing prices increased the most in the Western and Southern United States, while in the Northeast prices grew slowly, or declined.

Based on median single-family home price changes over the year through the second quarter from the NAR, 24/7 Wall St. reviewed the fastest growing (and shrinking) housing markets. The Boulder, Colorado area leads the nation with home prices rising 18.5% over the year. Home prices are down 13.1% in the Atlantic City-Hammonton, New Jersey region, the largest decline.

Click here to see the 25 fastest growing housing markets.

Click here to see the 25 fastest shrinking housing markets. 

In an interview with 24/7 Wall St., Danielle Hale, managing director of housing research at the NAR, said, “It’s good to think of [real estate] as being a life cycle product.” Young people with relatively unestablished careers and unsettled families typically rent to remain mobile. Once they become more established, they tend to transition into homeownership. “And they don’t often transition back into renting,” Hale noted.

Rising home prices are obviously a good thing for current owners, and also stimulate the economy. According to the “The State of the Nation’s Housing 2016,” a report by the Joint Center for Housing Studies of Harvard University, when home equity grows, owners spend more on home improvement projects and consumer spending increases in households.

One measure of the economy, the unemployment rate, appears to be tied to home prices. The percentage of the labor force looking for work fell over the year in June across the nation, particularly in growing housing markets. The jobless rate fell in all but one of the 25 fastest growing markets, while in nine of the 25 shrinking markets, the jobless rate actually increased.

To encourage the economic effects of a healthy housing sector, the Federal Reserve has kept interest rates low. The resulting low mortgage rates have helped encourage home purchases and boosted housing prices. However, home prices have risen about twice as fast as incomes over the past 12 months. For this and many other reasons, Hale explained that, while additional equity is great news for homeowners, the rising prices (and stagnant wages) make purchasing a home far more challenging for potential buyers.

The two largest hallmarks of fast-growing — and fast shrinking — markets are inventory levels and location, according to Hale. The NAR has tracked year-over-year inventory declines in each of the past 13 months. This means that there may be multiple offers on a single property, further driving up the original listing price. High demand, coupled with low new home construction rates, are the main drivers of the low inventory.

Demand for homes in particular locations is also a major factor in home price increases. More than half of the 25 fastest growing housing markets are located either in California or Florida. Hale noted that favorable climate in California and the West has always drawn Americans looking to relocate. The enormous success of California’s tech industry has further enhanced the appeal. In Florida, she added, lifestyle factors can be even more important than labor market factors, especially for retirees.

While California is home to some of the nation’s most expensive homes, Florida’s median home prices are fairly low even after nation-leading growths in a number of the state’s housing markets.

To identify the 25 fastest growing (and 25 fastest shrinking) housing markets, 24/7 Wall St. reviewed the largest and smallest home price changes over the 12 months through the second quarter of this year. Single-family home price data for the 180 metropolitan areas reviewed came from the NAR. Unemployment rates for metropolitan areas are for June 2016 from the Bureau of Labor Statistics.

These are the fastest growing (and shrinking) housing markets.