Clear Channel ( CCU) boosted its quarterly dividend and doubled its stock-buyback plan.The company said it would buy back an additional $1 billion in stock over the next year. Clear Channel has bought back $934 million in stock under a previous authorization. The advertising company also raised its quarterly dividend by 25% to 12.5 cents. The new rate is payable Oct. 15 to holders of record Sept. 30. "We continue to believe that the purchase of our common stock at the current stock price represents an attractive opportunity to benefit the long-term interests of the Company and its shareholders," CEO Mark Mays said. Clear Channel sank 57 cents Wednesday to $34.23.