Global Assault on Banks Intensifies

Credit Suisse Group AG shares plunged to the lowest in a generation on Thursday and a one-year contract to insure Deutsche Bank AG debt against default surged to a record as a global rout in financial companies intensified.

Theories abound as to what lies behind the months-long selloff, with some traders fretting over falling oil prices, China’s economy and negative interest rates. A pullback by some sovereign-wealth funds has also been blamed for lower asset prices. Whatever the cause, the hammering has been the worst in Europe, where concerns persist about the health of some of the biggest banks eight years after the financial crisis.