After steadily increasing for three straight months, pending home sales let up in May and declined year-over-year for the first time in almost two years, according to the National Association of Realtors®. All four major regions experienced a cutback in contract activity last month.

The Pending Home Sales Index, a forward-looking indicator based on contract signings, slid 3.7 percent to 110.8.

Lawrence Yun, NAR chief economist, says pending sales slumped in May across most of the country. “With demand holding firm this spring and homes selling even faster than a year ago, the notable increase in closings in recent months took a dent out of what was available for sale in May and ultimately dragged down contract activity,” he said.

“Realtors® are acknowledging with increasing frequency lately that buyers continue to be frustrated by the tense competition and lack of affordable homes for sale in their market.”

Impact of Brexit

Looking ahead to the second half of the year, Yun says the fallout from the U.K.’s decision to leave the European Union breeds both immediate opportunity as well as potential headwinds for the U.S. housing market.

“In the short term, volatility in the financial markets could very likely lead to even lower mortgage rates and increased demand from foreign buyers looking for a safer place to invest their cash,” he said. “On the other hand, any prolonged market angst and further economic uncertainty overseas could negatively impact our economy and end up tempering the overall appetite for homebuying.”

In spite of last month’s step back in contract signings, existing-home sales this year are still expected to be around 5.44 million, a 3.7 percent boost from 2015. After accelerating to 6.8 percent a year ago, national median existing-home price growth is forecast to slightly moderate to between 4 and 5 percent.