The Dow Jones Industrial Average on Thursday afternoon was trading near session lows, a day after the index booked the sharpest single-session point rally in its history. The Dow, most recently, was down 573 points, or 2.5%, at 22,302, with the other major indexes also headed sharply lower on the day. The S&P 500 index SPX, +1.59% fell 2.6% at 2,402, while the Nasdaq Composite Index COMP, +2.26% declined 3.1% in broad-market selling at 6,350. The moves highlight a regime of outsize volatility on Wall Street coming in the last several trading sessions of 2018. On Wednesday, the Dow ended with a gain of 1,086.25 points, or 5%, at 22,878.45. The S&P 500 soared 5% to end at 2,467.70. The Nasdaq rose 5.8% to 6,554.36