Warren Gardiner
Chief Financial Officer at Intercontinental Exchange
Thanks, M.C. Good morning, everyone, and thank you for joining us today. I'll begin on Slide four with some of the key highlights from our second quarter results. Adjusted earnings per share totaled $1.16, up 12% year-over-year. Net revenues totaled $1.7 billion, and on a pro forma basis, we're up 4% versus last year. While total transaction revenues declined slightly, our recurring revenues, which now represent over half of our business, increased by 10%, with all three of our business segments contributing to the strong year-over-year growth. Adjusted operating expense totaled $744 million. Our investment in Bakkt contributed approximately $36 million to second quarter expenses and were offset by approximately $9 million of net revenues.
We now anticipate that the Bakkt announced transaction with Victory Park will close in the third quarter. Looking to the second half, we expect third quarter adjusted operating expense to be in the range of $770 million to $780 million, including $55 million related to back which we expect will be offset by $12 million of net revenue. Incorporating third quarter Bakkt expense into our full year guide we now expect 2021 adjusted operating expenses to be in the range of $2.95 billion to $2.98 billion. First half free cash flow totaled over $1.4 billion, which was used to fund a 10% increase in our dividend while also reducing our leverage, ending the quarter at just under 3.4 times adjusted EBITDA. As noted last quarter, we elected to sell our stake in Coinbase in early April, generating over $1.2 billion in gross proceeds, which we then use to reduce commercial paper outstanding. With respect to our other minority investments, we are in the early stages of exploring a sale of our stake in Euroclear.
While the timing of any potential sale remains unclear, -- our strategy is consistent with our goal to reduce leverage following the acquisition of Ellie Mae and our strategic approach of continuously evaluating and optimizing the allocation of capital across our business. Now let's move to Slide five, where I'll provide an overview of the performance of our Exchange segment. Second quarter net revenues totaled $909 million, including $582 million of transaction revenues.
This strong performance was driven by a 6% increase in our interest rate business, an 11% increase in European natural gas revenues and a 59% increase in revenues related to global environmental products. Importantly, total open interest, which we believe is the best indicator of long-term growth is up 14% versus the end of last year, including 10% growth in energy open interest and 21% growth across our financial futures and options complex. Recurring revenues, which include our exchange data services and our NYSE listings business increased 7% year-over-year. The acceleration in growth was driven by 8% growth in our listings business. It is an increasing number of operating company IPOs, particularly in the technology and consumer sectors are joining the NYSE. Looking to the third quarter, we expect recurring revenues in our Exchange segment to be between $324 million and $329 million, representing approximately 5% growth year-over-year. As a sequential improvement in listings revenues is expected to be somewhat offset by lower data fees at the NYSE.
Turning now to Slide six. I'll discuss our Fixed Income and Data Services segment. Second quarter revenues totaled $458 million, 6% growth in our recurring revenues, which accounted for nearly 90% of total segment revenues offset a year-over-year decline in transaction fees. Fixed income data and analytics, which includes our leading pricing and reference data and ICE Data indices increased by 5%, including another quarter of double-digit growth in our index franchise. Other data and network services grew 7%, driven by continued customer demand for additional network capacity. Looking to the third quarter, we expect our recurring revenues to improve sequentially to a range of $409 million to $414 million. And in addition, we now expect full year recurring revenue growth to be towards the higher end of the 5% to 6% guidance range we provided on our fourth quarter call. Let's go next to slide 7, where I will discuss our Mortgage Technology segment. Please note that my comments on revenue growth are on a pro forma basis.
Mortgage Technology revenues grew 17% year-over-year. Second quarter transaction revenues increased by 8%, while recurring revenues were up 36% and at a $136 million exceeded the high end of our guidance range. These better-than-expected results were driven by a combination of new customer growth and increased adoption of digital workflow tools across origination technology, closing solutions and data and analytics. Shifting to the third quarter, we expect the recurring revenues will once again grow sequentially and be in the range of $137 million to $142 million, representing around 30% growth versus last year.
The first half of 2021 was the strongest in our company's history. We once again grew revenues, operating income and free cash flow. Adjusted earnings per share of $2.50 were up 9% versus the prior record set in the first half of 2020 and have increased 17% on average versus the first half of 2019. In addition, less than one year following our strategic acquisition of Ellie Mae, we have reduced debt by nearly $3 billion while also continuing to strategically invest in future growth.
I'll now turn the call over to Ben to discuss some of the highlights of our Exchange and Mortgage businesses.