I.B.M. Plans $15 Billion Share Buyback

I.B.M. said on Tuesday that its board had authorized a $15 billion share buyback program that could increase 2008 earnings by up to 5 cents a share, sending its stock up 4.2 percent.

News of the planned repurchase, equivalent to about 10 percent of the market capitalization of I.B.M., pushed the stock market higher. The company’s shares rose $4.30, to $114.38.