Following news about a bribery scandal involving its subsidiary in Mexico, Walmart’s stock price had its worst day in more than three years Monday, as prices fell 4.7% to $59.54. The decline helped push the Dow Jones Industrial Average back below 13,000. The scandal already threatens to ensnare the global giant’s top management. And the problems appear only to be multiplying, with two U.S. lawmakers on Monday launching an investigation and requesting an in-person meeting with compa...