Seemingly unrelated areas of the market are trading in the same direction more frequently than normal, a trend that some investors say is contributing to recent volatility and could drive more gyrations in the future. The S&P 500’s 11 sectors have either risen or fallen together during 11 trading sessions in August, the highest monthly incidence of such alignment since January 2016. Other risky investments such as commodities and global stocks have generally been tracking moves in U.S. stocks. (Wall Street Journal)