JPMorgan Chase, the largest bank in the United States, said Thursday that it lost $2 billion in the past six weeks in a trading portfolio designed to hedge against risks the company takes with its own money. The company’s stock plunged almost 7% in after-hours trading after the loss was announced. Other bank stocks, including Citigroup and Bank of America, suffered heavy losses as well. “The portfolio has proved to be riskier, more volatile and less effective as an economic hedge than we thought,” CEO Jamie Dimon told reporters. “There were many errors, sloppiness and bad judgment.” The trading loss...