A death cross is said to have occurred when the 50-day simple moving average, which many use to track the short-term trend, crosses below the 200-day moving average, which is widely used to gauge the health of the longer-term trend. For the Dow industrials, it marked the first time the 50-day moving average, which ended Tuesday at 17,806.99, was below the 200-day moving average, at 17,813.42, since Dec. 30, 2011, according to FactSet. Many technicians see the death cross as marking the spot that a shorter-term pullback morphs into a longer-term downtrend. The Dow followed Tuesday’s death cross by falling...