The number of contracts signed between Northern Virginia home buyers and sellers surged 90% in November compared to last year, just after Amazon.com Inc. AMZN, +1.94% announced plans to locate an additional headquarters in that area.

In November, 1,046 such contracts were signed, compared to 533 in November 2018, the Northern Virginia Association of Realtors said Friday. Pending sales — those that have entered into contract, cleared all contingencies, and are ready to proceed to close — were up 11.5%. “We believe these spikes may stem from one reason: the Amazon effect,” the Realtor association noted in a press release.