Wall Street ended a volatile August on a positive note. The three major indexes — the Dow, the S&P 500 and the Nasdaq Composite — were up 1.8%, 2.3% and 0.7%, respectively. Meanwhile, U.S. stock markets started September with a sharp decline. On Tuesday, the first trading day of this month, the Dow, the S&P 500 and the Nasdaq Composite — tumbled 1.5%, 2.1% and 3.3%, respectively.The situation is the same as in August, when U.S. stocks fell sharply in the first week of the last month. Despite a weak start to ...