Contracts to purchase previously owned homes unexpectedly dropped in January by the most in two years, representing a setback in residential real estate leading up to the spring selling season.

The pending home sales index fell 2.5 percent, the biggest drop since December 2013, after a 0.9 percent increase a month earlier that was larger than initially reported, the Washington-based National Association of Realtors said Monday. The median projection in a Bloomberg survey of economists called for the January index to rise 0.5 percent.

Still-tight credit conditions for some Americans, dwindling home choices and higher property prices could be limiting enthusiasm among prospective buyers. At the same time, persistent job gains, historically low mortgage rates and nascent signs of stronger wage growth should help keep housing from faltering.

“While January’s blizzard possibly caused some of the pullback in the Northeast, the recent acceleration in home prices and minimal inventory throughout the country appears to be the primary obstacle holding back would-be buyers,” NAR chief economist Lawrence Yun said in a statement. “Additionally, some buyers could be waiting for a hike in listings come springtime.”

Estimates in the Bloomberg survey of 33 economists ranged from a decline of 2.5 percent to an advance of 3.8 percent. The Realtors’ group revised the December data from an initially reported 0.1 percent increase.

Year Earlier

Purchase contracts dropped 0.9 percent in the 12 months ending in January after a 3.1 percent annual advance in December, the NAR report showed. The pending sales index was 106 on a seasonally adjusted basis, the lowest in a year. A reading of 100 corresponds to the average level of contract activity in 2001, or “historically healthy” home-buying traffic, according to the NAR.

Pending sales dropped in three of four regions, falling 4.9 percent in the Midwest, 4.5 percent in the West and 3.2 percent in the Northeast. Purchase contracts rose 0.3 percent in the South.

Economists consider pending sales a leading indicator because they track new purchase contracts. Existing-home sales are tabulated when a deal closes, usually a month or two later.

Those re-sales, which make up about 90 percent of the market, unexpectedly climbed in January to the second-highest pace since early 2007, NAR reported last week. Prices climbed from January 2015 as the number of dwellings on the market fell.