Existing home sales faltered in August after a red-hot four-month stretch of gains, a leading trade group said Thursday. According to the regular report by the National Association of Realtors, sales of prior-owned homes fell 2.7 percent since July, after a 15.2 percent climb since April. “This is an unpleasant surprise,” wrote one economist, Ian Sheperdson, at High Frequency Economics. As analysts debate whether an economic recovery is in effect, home prices and sales have been two factors that seemed to support the idea that the downturn is over. The most recent numbers, however, cast new doubt on the housing industry’s stability and the broader economy’s soundness. “The decline demonstrates we can’t take a housing rebound for granted,” NAR Chief Economist Lawrence Yun said in a press statement. The NAR figures closely match inventory data released this week by the national real estate broker ZipRealty. In its study, ZipRealty found that the number of homes listed for sale on the Multiple Listing Service also fell by 2.7 percent, the 14th straight month of declines. ZipRealty also registered serious housing inventory declines in a number of metropolitan areas — 7.6 percent in San Francisco, 5.1 percent in Orlando, Florida, and 4.7 percent in Washington.

Economists are puzzling over those numbers, especially the sales results reflected in the NAR report. Before August ended, analysts had a consensus that predicted 5.35 million unit sales on the month, which would have been an improvement of 110,000 units over the July totals. But instead, The NAR said home sales in August only amounted to a seasonally adjusted 5.1 million units, well short of both July and the projected August figures. Shepherdson said July pending sales — which should be a good predictor of actual sales — indicated the August total should have been around 5.4 million units. “The gap between the two numbers is not unprecedented, but we had hoped for better,” he said. The NAR report also highlighted the role distressed properties — especially short sales and foreclosures — were playing in driving down median home prices across the board. Such properties — which typically move for 15 or 20 percent less than more traditional residences — made up about a third of August’s home resales. Still, Shepherdson said the distressed sales and price dips couldn’t fully explain the August report’s sales numbers. “It could just be noise; we await the next pending sales index with some trepidation,” he said.