WASHINGTON (Reuters) - Contracts to buy previously owned homes were flat in September and activity declined on an annual basis for the fifth time in the last six months as demand for properties continued to exceed supply.

FILE PHOTO: A townhouse for sale that is currently under contract is seen in Bethesda, Maryland December 30, 2015. REUTERS/Gary Cameron

The National Association of Realtors said on Thursday its Pending Home Sales Index, based on contracts signed last month, was unchanged with a reading of 106.0. August’s index was revised lower.

Economists polled by Reuters had forecast pending home sales edging up 0.2 percent last month.

Pending home contracts are viewed as a forward-looking indicator for the state of the housing market because they become sales one or two months later.

Although the U.S. economy continues to strengthen, the housing sector has faltered this year. Home sales have weakened amid tight inventories while builders have cited shortages of land and labor as a curb on construction.

Compared to one year ago, pending sales fell 3.5 percent overall and there were annual declines across all four of the nation’s regions.

Compared with the prior month, pending sales for September rose 1.2 percent in the Northeast, 1.4 percent in the Midwest and 1.9 percent in the West.

“Activity is falling further behind last year’s pace because new listings aren’t keeping up with what’s being sold,” NAR chief economist Lawrence Yun said in a statement.

He added the situation will likely be further exacerbated as inventory starts to decline heading into the winter months.

The South saw declines of 2.3 percent in September, which the NAR largely attributed to the effects of Hurricanes Harvey and Irma.