Contract signings to purchase previously owned U.S. homes unexpectedly fell in September by the most since the end of 2013, indicating the residential real estate market is cooling from its recent brisk pace.

An index of pending home sales dropped 2.3 percent in September after a 1.4 percent decline a month earlier, the National Association of Realtors said Thursday. The decrease exceeded the most pessimistic forecast in a Bloomberg survey of economists.

A limited selection of properties may be dissuading some from trading up, while stricter credit standards are making it difficult for others to qualify for loans. At the same time, housing demand will probably be underpinned by cheap borrowing costs and employment opportunities.

“There continues to be a dearth of available listings in the lower end of the market for first-time buyers," NAR chief economist Lawrence Yun said in a statement. Still, “with interest rates hovering around 4 percent, rents rising at a near eight-year high, and job growth holding strong — albeit at a more modest pace than earlier this year — the overall demand for buying should stay at a healthy level.”

The median forecast in the Bloomberg survey of 35 economists called for a 1 percent gain, with estimates ranging from a 1 percent decrease to a 2.5 percent advance.

Year Earlier

Purchase contracts were up 2.5 percent in the 12 months ended in September on an unadjusted basis after a 6.6 percent gain in the year through August, the NAR report showed.

The pending sales index was 106.8 on a seasonally adjusted basis, the lowest since January. 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 all four U.S. regions, led by a 4 percent decrease in the Northeast. Purchase contracts were down 2.6 percent in the South, 2.5 percent in the Midwest and 0.2 percent in the West.

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

Home re-sales, which make up about 90 percent of the market, rose in September to the second-highest level since 2007, the NAR reported last week. Inventories decreased 2.6 percent from a month earlier.

Pending sales are a barometer of future purchases. A lag of a month or two usually exists between a contract and a completed sale.