Update, January 7th, 3.50pm London: China's stock exchanges announced on Thursday evening that they would suspend use of the circuit-breakers. The securities regulator said they were not the main ...

—from an index’s recent high-water mark. And now, the Dow Jones Industrial Average, S&P 500, and Nasdaq Composite are all on the brink of entering one. Stocks sold off hard and fast on Monday, on ...