Stocks fell modestly in lower volume Monday amid weak Chinese economic data and uncertainty about whether the Federal Reserve will raise interest rates this week. The S&P 500 and the Dow Jones industrial average each slipped 0.4%, while the Nasdaq dipped 0.3%. Volume fell 13% on the Nasdaq and 6% on the NYSE compared with Friday, according to preliminary data, partly due to the start of Rosh Hashanah, the Jewish New Year.