Friday's release of the Purchasing Managers Index (PMI), which measures activity in the 88% of the economy not in manufacturing, show a decline in September. The non-manufacturing PMI dropped to 52.6 from August's 56.4 and from July's 53.7 reading.

From its highest reading in a decade achieved last September, the non-manufacturing sector, also known as the service economy, dropped to a rate in line with its long-term norm. At 52.6, the service economy in September was growing in line with its rate over the past decade since this index's inception in January of 2008, according to data from the Institute of Supply Management (ISM), which maintains the index. While this index has only limited history, the ISM non-manufacturing PMI is designed to substantially slump when there's a reading of less than 50 percent months in advance of the onset of a recession.

Anthony Nieves, chair of the ISM's services survey committee, said he wasn't yet overly concerned about a pullback in the services sector because the index's August reading was relatively high, the jobs market remains solid and the American consumer is holding up well. "Next month, especially with the retail holiday season coming, my prediction is that we should see increases in the rate of growth [for services], provided there aren't more developments with the trade war," Mr. Nieves said.