NEW YORK — The average U.S. stock market index fell about 0.5% Monday.That was about a tenth of a percentage point lower than the 0.6% drop last week.The Dow Jones industrial average fell about 566 points.The S&P 500 index fell 0.8%.The Nasdaq composite fell about 1%.The Russell 2000 fell 0 .2%.The Dow Jones Industrial Average…