Mark McGivney
Chief Financial Officer at Marsh & McLennan Companies
Thank you, Dan, and good morning. Our results were outstanding with record third quarter revenue, second consecutive quarter of double-digit underlying growth, margin expansion, and significant earnings growth. Highlights from our third quarter performance included a second straight quarter of 13% underlying growth in RIS, with 13% in Marsh and 15% in Guy Carpenter, and a second consecutive quarter of 12% underlying growth in Consulting, with 7% of Mercer and 25% at Oliver Wyman.
Growth in adjusted earnings per share exceeded 30% for the second quarter in a row. Consolidated revenue increased 16% in third quarter, $4.6 billion, reflecting underlying growth of 13%. Operating income in the quarter was $740 million, an increase of 37%. Adjusted operating income increased 19% to $759 million and our adjusted operating margin increased 10 basis points to 18.5%.
GAAP EPS was $1.05 in the quarter and adjusted EPS increased 32% to $1.08. For the first nine months of 2021, underlying revenue growth was 10%. Our adjusted operating income grew 21% to $3.4 billion. Our adjusted operating margin increased 120 basis points and our adjusted EPS increased 28% to $4.82.
Looking at Risk and Insurance Services. Third quarter revenue was $2.7 billion up 17% compared with a year ago or 13% on an underlying basis. Operating income increased 21% to $403 million. Adjusted operating income also increased 21% to $469 million and our adjusted operating margin expanded 20 basis points to 20.4%.
For the first nine months of the year, revenue was $9 billion with underlying growth of 11%. Adjusted operating income for the first nine months of the year increased 20% to $2.5 billion with a margin of 30.3%, up 80 basis points from the same period a year ago.
At Marsh, revenue in the quarter was $2.4 billion of 17% compared with a year ago or 13% on an underlying basis. Growth in the quarter was broad-based driven by nearly 40% new business growth and solid retention. U.S. and Canada delivered another exceptional quarter with underlying revenue growth of 16% and international underlying growth was 9%, Latin America grew 12%, its best growth since the fourth quarter of 2015, Asia-Pacific was up 9% and EMEA was up 8%.
For the first nine months of the year, Marsh's revenue was $7.3 billion with underlying growth of 12%. U.S. and Canada underlying growth was 14% and international was up 9%. Guy Carpenter's third quarter revenue was $314 million, up 15% compared with a year ago on both a GAAP and underlying basis. Growth was broad-based across geographies and specialties. Guy Carpenter has now achieved 7% or higher underlying growth in seven of the last nine quarters. For the first nine months of the year, Guy Carpenter generated $1.7 billion of revenue and 10% underlying growth.
In the Consulting segment, revenue in the quarter was $1.9 billion, up 13% from a year ago or 12% on an underlying basis. Operating income increased 45% to $404 million. Adjusted operating income increased 15% to $350 million. The adjusted operating margin was 18.9% in line with the margin in the third quarter of 2020. Consulting generated revenue of $5.7 billion for the first nine months of 2021, representing underlying growth of 9%. Adjusted operating income for the first nine months of the year increased 25% to $1.1 billion and the adjusted operating margin expanded 180 basis points to 19.6%.
Mercer's revenue was $1.3 billion in the quarter, up 7% on an underlying basis, the highest result in over a decade. Career grew 13% on an underlying basis, reflecting the continuing rebound in the global economy and business confidence. Wealth increased 6% on an underlying basis, reflecting strong growth in investment management and modest growth in defined benefit. Our assets under delegated management grew to nearly $400 billion at the end of the third quarter, up 24% year-over-year benefiting from net new inflows and market gains. Health underlying revenue was -- growth was 4% in the quarter, driven by growth outside the U.S.
Oliver Wyman's revenue in the quarter was $610 million, an increase of 25% on an underlying basis. This represents the second consecutive quarter of more than 20% growth as demand remains strong across most geographies and practices. For the first nine months of the year, revenue at Oliver Wyman was $1.8 billion, an increase of 21% on an underlying basis.
Adjusted corporate expense was $60 million in the third quarter. Foreign exchange had a negligible impact on earnings in Q3. Assuming exchange rates remain at current levels, we expect FX to be a modest headwind in the fourth quarter. Our other net benefit credit was $69 million in the quarter and we expect it will remain at this level in the fourth quarter. Investment income was $13 million in the quarter on a GAAP basis and $12 million on an adjusted basis, and mainly reflects gains on our private equity portfolio.
Interest expense in the third quarter was $107 million compared with $128 million in the third quarter of 2020, reflecting lower debt levels in the period. Based on our current forecast, we expect interest expense in the fourth quarter to be similar to the amount in the third quarter. Our adjusted effective tax rate in the third quarter was 24.4% compared with 26.5% in the third quarter last year.
Our GAAP tax rate was 24.2% in the third quarter, down from 30.3% in the third quarter of 2020 which was impacted by some unusual item. Through the first nine months of the year, our adjusted effective tax rate was 24.4% compared with 24.6% last year. Based on the current environment, we continue to expect an adjusted effective tax rate between 25% and 26% for 2021 excluding discrete items.
Given our year-to-date performance, we are on track for an outstanding year. Looking specifically at the fourth quarter, keep in mind the comparisons become more challenging given the rebound in growth in the fourth quarter of 2020. We also continue to build for the long-term by investing in hiring. While we are excited about the future benefits these investments will deliver, they come with upfront costs we absorb in the short-term. That said, we've consistently demonstrated our ability to deliver exceptional results today while investing for the future and expect we will continue to do so.
Turning to capital management or balance sheet. We ended the quarter with $10.7 billion of total debt. Our next scheduled debt maturity is in January of 2022 when $500 million of senior notes mature. We continue to expect to deploy at least $3.5 billion of capital in 2021, of which at least $3 billion will be deployed across dividends, acquisitions and share repurchases. The ultimate level of share repurchases will depend on how the M&A pipeline develops.
Our cash position at the end of the third quarter was $1.4 billion. Uses of cash in the quarter totaled $665 million and included $272 million for dividends, $93 million for acquisitions and $300 million for share repurchases. For the first nine months, uses of cash totaled $2.6 billion and included $750 million for dividends, $566 million for acquisition, $734 million for share repurchases and $500 million for debt repayment. We had a remarkable third quarter positioning us well to deliver strong growth in both revenue and adjusted earnings in 2021.
And with that, I'm happy to turn it back to Dan.