Wal-Mart ( WMT) set a new $5 billion stock buyback, replacing a previous $3 billion program, and said it would expense stock options on its earnings statement. Wal-Mart said it spent $1.7 billion to buy back shares during the first six months of its fiscal year. The company does its repurchases occasionally in the open market and in transactions negotiated privately. In addition to the options expensing, which it predicted would cost it less than a penny a share in yearly earnings, Wal-Mart said its chief executive and chief financial officer signed sworn certifications that the company's financial statements are accurate. The shares were recently trading up 7.8% to $52.51.