Global stocks tumbled, led by bank shares, as concern swept through financial markets that a widening credit crunch may hurt economic growth and earnings. Countrywide Financial Corp., the biggest U.S. mortgage lender, slid after saying “unprecedented disruptions” may crimp profit. Societe Generale SA fell, while ABN Amro Holding NV dropped the most since 2003 on speculation financial-market turmoil may derail the world’s biggest banking takeover. Macquarie Bank Ltd. paced declines in Asia. [MORE]