Twitter Inc. announced a major restructuring effort Thursday, dividing the company into groups that are focused on functions instead of a general manager structure, Chief Executive Jack Dorsey said in a series of tweets. Twitter stock was up 2.6% to $44.84 in late-afternoon trading. Dorsey said that the change is necessary to ensure that Twitter can plan for the next decade and ensure the company "continue[s] to be relevant and important for the world." Twitter stock is up 87% this year, as the S&P 500 index is up 1.8%.