There will be 20.1 percent fewer homes available on the market in the Seattle metro area this year than in 2017, part of nationwide inventory shortage that Zillow describes as "approaching crisis levels" in some of the nation’s hottest housing markets.

According to Zillow's December market report released Thursday, the median home value in Seattle is $468,000. That's up 12.5 percent over the past year.

Because of the tight demand, 52.4 percent of Seattle homes sold for more than the asking price in 2017.

Nationwide, there are 10 percent fewer homes on the market than year ago. Unless more homes are built, economists say they don't see the trend changing, according to Zillow. The median U.S. home value rose 6.5 percent over the past year to $206,300. Zillow said that's highest it has ever been.

“Tax reform will put more money in the pocket of the typical buyer, but will limit some housing-specific deductions. Overall, this should increase demand for the most affordable homes and ease competition somewhat in the priciest market segments," Zillow senior economist Aaron Terrazas said in a statement.

Terrazas said more affordable homes might be found for sale in 2018, but in areas well outside of urban centers, like Seattle, that will require buyers to plan for more brutal commutes.

The two cities that saw home prices increase at a higher rate were San Jose (21.2 percent) and Las Vegas (14.3 percent).

It's bad for renters, too. The median rent is $2,203 per month, up 5.2 percent over the past year. The good news for renters: Zillow said that's the slowest rent appreciation in Seattle in almost three years. The bad news: That's the third-highest rate in 2017 for the markets Zillow tracked (Sacramento was No. 1 at 7.9 percent and Riverside, Calif. was No. 2 at 6.1 percent).