Japan's Nikkei 225 index plunges 12.4% as world markets tremble over risks to the US economy

The Nikkei 225 dropped 5.8% on Friday, making this its worst two-day decline ever. Its worst single-day rout was a plunge of 3,836 points, or 14.9%, on a day dubbed “Black Monday” in October 1987. At one point, the benchmark sank as much as 13.4% on Monday. Share prices have fallen in Tokyo since the Bank of Japan raised its benchmark interest rate on Wednesday. The Nikkei is now down 3.8% from a year ago. One factor driving the BOJ to raise rates was prolonged weakness in the Japanese yen,...