BlackRock Inc. (BLK) earned $551 million, or $2.83 a share, for the third quarter up from $317 million, or $2.27 a share, a year ago. Revenue for the three months ended Sept. 30 rose 84% to nearly $2.1 billion from $1.14 billion last year. The investment advisor said third-quarter results were helped by the acquisition of Barclays Global Investors and "improved markets." "BlackRock’s robust third-quarter results reflected the breadth of our business globally, strong performance in both index and actively managed products, and increasing demand for BlackRock’s unique ability to deliver multi-asset class and risk management solutions to our clients," according to chairman and chief executive Laurence Fink. "Expansion of our operating margin, particularly given the level of investment we are making in the business, reflects the leveragability of our platform and our continued focus on managing expenses," Fink said. Boosted by the purchase of Barclays, which closed in December, Blackrock has the most assets under management of any firm in the world with $3.45 trillion. At Sept. 30 a year ago, Blackrock had about $1.43 trillion of assets under management. Write to Jason Philyaw. The author holds no relevant interests.