Private sector employment increased by 178,000 jobs from April to May according to the May ADP National Employment Report.

"The hot job market has cooled slightly as the labor market continues to tighten," said Ahu Yildirmaz, vice president and co-head of the ADP Research Institute. "Healthcare and professional services remain a model of consistency and continue to serve as the main drivers of growth in the services sector and the broader labor market as well."

Mark Zandi, chief economist of Moody's Analytics, said, "Job growth is strong, but slowing, as businesses are unable to fill a record number of open positions. Wage growth is accelerating in response, most notably for young, new entrants and those changing jobs. Finding workers is increasingly becoming businesses number one problem."