Taking a look at the summary results for the quarter. Assets under management ended the quarter at $672 billion versus $625 billion at the end of 2011. Invesco continued to generate a strong long-term investment performance for our clients during the quarter, which contributed to the net long-term inflows of $7 billion. This further extended the positive trend that we've demonstrated over the last several quarters.
Operating income rose to $269 million versus $256 million in the fourth quarter last year. The operating margin was 36.6% during the first quarter, again, expanding over the fourth quarter operating margin of 35.8%.
Earnings per share for the quarter were $0.44 per share, up approximately 5% quarter-over-quarter. And again, Loren will go into a much greater detail with the financial results.
Let's take a moment and look at investment performance, and again, it's our continued commitment to investment excellence and the hard work to build and maintain the culture. The strong investment culture has generated this strong long-term investment performance across the enterprise. And if you take a look over at the firm as a whole, 65% of the assets were ahead of peers on a linear basis and 77% of assets were ahead of peers on a 5-year basis.And as we mentioned the last quarter, the softness in the 3-year number reflects the rolling off of some very strong numbers in the fourth quarter 2008 and a brief period where we trail the market during that snapback data rally in the early part of 2009. Based on the strength of the recovery later in that year in 2009, we would expect that 3-year numbers to solidify in mid-2012. Moving on to flows, again strong investment performance contributed to positive inflows in spite of the volatile markets. And as I've mentioned earlier, net long-term inflows totaled $7 billion for the quarter. During the first quarter, we saw a strong client interest in the Balanced-Risk Allocation product, real estate capabilities, ETFs and also in our [indiscernible] International Equity, bank loans, maintaining, Muni [Municipal], stable value. So it was really some broadness in the interest across the organization.