After years of steeply rising prices and tight supply, U.S. homebuyers are getting a bit of relief. The inventory of houses on the market has climbed nationally for four out of the last five months, according to a report from Zillow.

One glaring exception to the trend: Washington, D.C. Listings there plunged 20 percent in January from a year earlier, Zillow said, marking a third straight month of double-digit declines.

Inventory data can be noisy and influenced by many factors. But, as Zillow points out, the recent change in Washington coincides with Amazon.com Inc.’s announcement in November that it would set up a new headquarters across the Potomac River in Northern Virginia, along with a pledge to employ more than 25,000 people there over time. Speculators immediately looked to scoop up homes, even though it will take time for Amazon to staff up in the area.

Some research has shown that Amazon’s impact on the Washington-area housing market will be gradual and dispersed. But if the trend toward tighter inventory continues, it could be a headache for the company in a community where it’s generally been greeted warmly.

Amazon has faced criticism in its hometown of Seattle, where the firm’s growth has dovetailed with a tight housing market and affordability crisis. The business is also facing a backlash in New York, where it’s planning a new office hub as well. Housing inventory in the Big Apple, though, climbed 5.5 percent over the past year, Zillow found.