Economic activity in the manufacturing sector expanded in November for the 18th consecutive month, but at a slower pace, according to the nation’s supply executives in the latest survey by the Institute for Supply Management

The November Purchasing Managers Index registered 58.7%, a decrease of 0.3 of a percentage point from October’s reading of 59%, which tied the level from August and was the highest since March 2011. A reading above 50% indicates expansion while one below 50% shows contraction.

The New Orders Index registered 66%, an increase of 0.2 of a percentage point from the reading of 65.8% in October. ISM’s New Export Orders Index registered 55% in November, which is 3.5 percentage points higher than the 51.5% reported in October. November’s reading reflects growth in the level of exports for the 24th consecutive month.

“Comments from the panel are upbeat about strong demand and new orders, with some expressing concerns about West Coast port slowdowns and the threat of a potential dock strike,” said Bradley J. Holcomb, chair of the Institute for Supply Management Manufacturing Business Survey Committee.

Of the 18 manufacturing industries, 14 reported growth in November.