The Dow Jones Industrial Average finished the trading day down 611 points, a blistering reaction to the United Kingdom’s decision to leave the European Union. At the start of the trading day, it plummeted more than 400 points as global markets were reeling from the results of the referendum. The index closed 3.39 percent in the red, erasing its 2016 gains. In the U.S., crude oil futures dropped nearly 5 percent to $47.64 per barrel. Before trading even began in the U.S., the British pound fell to a 31-year low overnight.