The S&P 500 notched a fourth straight drop of at least 1.5 percent, a run of futility not seen since August 2015. It's now down more than 19.8 percent from its September record and on pace for the worst monthly drop since 2008. Trading was 41 percent above the 30-day average in a session that's normally subdued ahead of the Christmas holiday. The stock market closed at 1 p.m.