By John S. McClenahen If Federal Reserve chairman Alan Greenspan and his colleagues on the Federal Open Market Committee decide to raise short-term interest rates in two weeks, they'll have to base it on something other than July's U.S. employment data. The nation's total nonfarm payroll employment declined by 108,000 between June and July to 131.5 million persons, reports the U.S. Labor Dept.'s Bureau of Labor Statistics. Within the private sector, which includes manufacturing and construction, employment grew by 138,000. But that's dramatically lower than the 182,000 average monthly increase for this year's first six months. Employment in manufacturing grew by 46,000 people in July, spurred mainly by producers of electronic components and instruments. Construction-industry employment grew by 6,000 people in July, but the average so far this year has been 17,000 a month, compared with 25,000 per month during economically faster-paced 1999. "The July employment report was nearly perfect," says Bruce Steinberg, chief economist at Merrill Lynch Co., New York. "Growth has moderated, productivity is awesome, and labor market strains are easing. The report reinforces our belief that the Fed is finished tightening."