ByJohn S. McClenahen U.S. personal income, disposable personal income and personal consumption expenditures all increased again in August, according to the most recent data from the U.S. Commerce Department. However, the long-expected slowdown in consumer spending, which accounts for about two-thirds of U.S. economic activity, seems to be under way. Personal income expenditures in August increased 0.3% ($23.7 billion), not as much as the 0.5% gain that economists generally expected and well below July's 1% increase. "Spending is likely to remain sluggish into the winter, victim of a weak job market, rising oil prices, and war jitters," says Bruce Steinberg, chief economist at Merrill Lynch & Co., New York. "In the near term, the proceeds from the mortgage-refinancing boom should bridge the period until job growth resumes. But, ultimately, the job market must strengthen to keep spending rising."