. on march 16 , 2006 , the board authorized a new program for the purchase of up to 15 million shares of our common stock for general corporate purposes , including mitigating the dilutive impact of shares issued under employee benefit programs , and terminated the 2005 program . under this new program , we purchased 2.8 million shares of our common stock during 2006 , and as of december 31 , 2006 , 12.2 million shares were available for purchase