Since closing our acquisition of JLT, we've grown our total consolidated revenue by 27%, our adjusted earnings per share by 34% and our colleague base by 22%.
We grew our headcount year-to-date by nearly 5,000 or around 7%, mostly organic adds with an emphasis on client-facing roles.
The Marsh Global Insurance Market Index showed price increases of 15% year-over-year consistent with second quarter.
The Marsh market index showed global property insurance was up 9%.
Global, financial and professional lines were up 32% driven in part by a near doubling in cyber rates, and global casualty rates were up high single-digits on average.
We generated adjusted earnings per share of $1.08, which is up 32% versus a year ago, driven by strong top-line growth and continued low levels of T&E.
Total revenue increased 16% versus a year ago and rose 13% on an underlying basis, the second consecutive quarter of record underlying growth in over two decades.
Underlying revenue grew 13% in RIS and 12% in Consulting.
Marsh grew 13% in the quarter on an underlying basis and benefited from strong new business and renewal growth.
Guy Carpenter grew 15% on an underlying basis in the quarter continuing its string of excellent results.
Mercer underlying revenue grew 7% in the quarter, the highest in over a decade.
Oliver Wyman grew underlying revenue 25%, the second consecutive quarter in excess of 20%.
Overall, the third quarter saw adjusted operating income growth of 19% and our adjusted operating margin expanded 10 basis points year-over-year.
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 earnings per share was $1.05 in the quarter and adjusted earnings per share 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 earnings per share increased 28% to $4.82.
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.
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.
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.
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.
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.
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.
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.

Summary:
We generated adjusted earnings per share of $1.08, which is up 32% versus a year ago, driven by strong top-line growth and continued low levels of T&E.
Consolidated revenue increased 16% in third quarter, $4.6 billion, reflecting underlying growth of 13%.
GAAP earnings per share was $1.05 in the quarter and adjusted earnings per share increased 32% to $1.08.