Real estate firm Redfin named Arlington County and Alexandria in Virginia as America’s two most competitive markets for potential home buyers.

Redfin looked at markets across the country to determine the highest number of competing offers and waived contingencies, how quickly homes are going under contract and for how much above list price.

Arlington County and Alexandria scored 96 out of 100, meaning both are where potential buyers are facing the most intense competition anywhere in the country.

Redfin points at Amazon’s HQ2 as one factor boosting the two markets, which are closest to the tech giant’s future site at Crystal City.

“The Amazon HQ2 effect has become a permanent factor in the Arlington and Alexandria housing markets,” said local Redfin agent Marcia Burgos-Stone.

“Some sellers are still opting to hold on to their homes and wait until it becomes a more concrete reality in the hopes that they will get more money. This has led to a shortage of homes for sale.”

The number of active listings in both Arlington and Alexandria is currently about half what it was a year ago.

Homes sold in July in Arlington County were on the market a median 11 days, and a median 14 days in Alexandria, a week less than a year ago and well below the 27-day median for the D.C. metro area.

More than half of homes for sale in Arlington and Alexandria went off the market in two weeks or less, compared to 29% nationwide.

In July, 46% of homes in Arlington that sold went for more than list price. In Alexandria, 36% sold for more than list.

“A market can become highly competitive when buyers agree that home values will increase steeply in the future,” said Redfin chief economist Daryl Fairweather. “If you believe home values will go up hundreds of thousands of dollars in the next five years, you will race to bid 5,000 or $10,000 above asking price today.”

It is expected to take a decade or longer for Amazon’s HQ2 to grow to the size of its Seattle headquarters.