ByJohn S. McClenahen The monthly measure of manufacturing activity from the Tempe, Ariz.-based Institute for Supply Management (ISM) is among the most closely watched of U.S. economic indicators. So it's natural that ISM's latest semiannual economic forecast, released Dec. 9, would command more than passing attention. That forecast shows economic growth in the U.S. strengthening in 2004, with purchasing and supply executives in both the manufacturing and non-manufacturing sectors of the economy more optimistic about the coming year than they were a year ago about 2003. For 2004, the executives foresee revenue growing 5.8% among manufacturers, more than double the 2.8% expected for this year; capital spending up 3.2% compared with 2.7% this year; and capacity utilization at 80.1%. For non-manufacturing, the executives forecast 5.7% revenue growth, a 7.1% increase in capital spending, and capacity utilization at 85.6%. Manufacturing industries expected to show the greatest year-over-year improvement in 2004 are (in order) electronic components and equipment; transportation and equipment; primary metals; textiles; instruments and photographic equipment; furniture; rubber and plastic products; food; wood and wood products; glass, stone and aggregates; printing and publishing; and a miscellaneous group that includes, jewelry, toys, sporting goods and musical instruments.