Business activity in the United States in September grew at its slowest monthly pace in 12 months, with supply chain hold-ups and capacity shortages hampering growth. Data firm IHS Markit said on Sept. 23 that its flash U.S. Composite PMI Output Index (pdf)—which tracks the manufacturing and services sectors—retreated to a reading of 54.5 in September. That’s a drop of one percentage point from August’s reading of 55.5 and the lowest level in 12 months. A reading above 50 indicates growth in private sector output. “The pace of U.S. economic growth cooled further in September, having soared in the second quarter, reflecting a combination of peaking demand, supply chain delays, and labor shortages,” Chris Williamson, Chief Business Economist at IHS Markit, said in a statement. Hiring difficulties weighed on business activity, with firms reporting only a slight rise in employment for the second month in a row. Trucking issues and …