The implied volatility for the next 30 days on Apple options rose 9 percent to 25.3 percent, reflecting more risk for Apple shares in the near term." In addition to his stake, Icahn tweeted that he discussed increasing Apple's buyback program with Chief Executive Officer Tim Cook. August options which expire on Friday after the close represented 52 percent of Apple's turnover. Apple options volume also accounted for 11.6 percent of the total single stock options volume for the day, data from Trade Alert showed.