Pending home sales fell slightly in August and have now decreased on an annual basis for eight straight months, according to the National Association of Realtors.

The Pending Home Sales Index, a forward-looking indicator based on contract signings, decreased 1.8 percent to 104.2 in August from 106.1 in July. With last month's decline, contract signings are now down 2.3 percent year-over-year.

Lawrence Yun, NAR chief economist, says that low inventory continues to contribute to the housing market slowdown. "Pending home sales continued a slow drip downward, with the fourth month over month decline in the past five months," he said.

"Contract signings also fell backward again last month, as declines in the West negatively impacted overall activity," he said. "The greatest decline occurred in the West region where prices have shot up significantly, which clearly indicates that affordability is hindering buyers and those affordability issues come from lack of inventory, particularly in moderate price points."