Though stocks fell on Wednesday after a surprising contraction in an index of Midwest business activity, the Dow Jones industrial average for the third quarter marked its biggest quarterly gain since the fourth quarter of 1998. The Dow Jones industrial average dropped 29.92 points, or 0.31 percent, to end unofficially at 9,712.28. The Standard & Poor's 500 Index fell by 3.53 points, or 0.33 percent, to finish at 1,057.08. The Nasdaq Composite Index fell by 1.62 points, or 0.08 percent, to close at 2,122.42. The New York Stock Exchange fell by nearly 16 points or 0.23 percent to 6,910. The American Exchange composite was up nearly 9 points to 1,778.67, and the Russell 2000 went down by 6.17 points, or 1.01 percent, to 604.28. Light sweet crude for November delivery rose by $3.90 to end at $70.61 a barrel. For the third quarter, the Dow rose 15 percent, the S&P 500 gained 15 percent and the Nasdaq climbed 15.7 percent. For the month of September, the Dow rose 2.3 percent, the S&P 500 gained 3.6 percent and the Nasdaq climbed 5.6 percent. These gains ran counter to historic trends showing that September often a tough month for stocks.