Chief Financial Officer and Executive Vice President of Global Finance at AON
Thanks so much, Greg, and good morning, everyone. As Greg highlighted, we delivered another strong quarter performance across our key metrics to finish the year. In the quarter, we delivered 10% organic revenue growth, the third consecutive quarter of double-digit organic growth, which translated into double-digit adjusted operating income and adjusted earnings per share growth, continuing our momentum as we head into 2022.
As I reflect on full-year results: first, organic revenue growth was 9%, including double-digit growth in Commercial Risk Solutions and Health Solutions. I would note the total revenue growth of 10% includes a modest favorable impact from changes in FX, partially offset by the impact of certain divestitures completed within the year, most notably the retiree health care exchange business, as we continue to shift our portfolio towards our highest growth and return opportunities.
As we look to 2022, we're continuing to monitor various macroeconomic factors, including the underlying driver of GDP, asset values, corporate revenues and employment, inflation, government stimulus and the impacts of COVID variant, all of which impact our clients and our business. We continue to expect mid single-digit operational organic revenue growth for 2022 and over the long-term.
Moving to operating performance, we delivered substantial operational improvement with adjusted operating income growth of 17% and adjusted operating margin expansion of 160 basis points to a record 30.1% margin. The investments we've made in Aon Business Services give us further confidence in our ability to expand margins, building on our track record of approximately 100 basis points average annual margin expansion over the last decade.
We previously described the repatterning of expenses that incurred within 2021, which has no impact on year-over-year margins. While certain expenses may move from quarter-to-quarter, we do not expect further repatterning. We expect the 2021 expense patterning to be the right quarterly patterning going forward, before any expense growth.
During the year, as we previously communicated, we saw revenue growth outpaced expense growth and investments. While we do expect expenses to increase in 2022, due to certain factors such as increased investments in colleagues and a modest resumption of T&E, we think about growing margins over the course of a full-year. We expect to deliver margin expansion in 2022, as we continue our track record of cost discipline and managing investments in long-term growth on ROIC basis.
We translated strong adjusted operating income growth into double-digit adjusted EPS growth of 22% for the full-year, building on our track record of double-digit adjusted EPS growth over the last decade. As noted in our earnings materials FX translation was an unfavorable impact of approximately $0.03 in the fourth quarter and with the favorable impact of approximately $0.23 per share for the full-year. If currency remains stable at today's rates, we would expect an unfavorable impact of approximately $0.16 per share or approximately $48 million decrease in operating income in the first quarter of 2022. In addition, we expect non-cash pension expense of approximately $11 million for full-year 2022, based on current assumptions. This compares the $21 million of non-cash pension income recognized in 2021.
Turning to free cash flow and capital allocation. We continue to expect to drive free cash flow growth over the long-term, based on operating income growth, working capital improvements and structural uses of cash enabled by Aon Business Services.
In 2021, free cash flow decreased 23% to $2 billion, reflecting strong revenue growth, margin expansion and improvements in working capital, which were offset by a $1 billion termination fee payment and other related costs. I'd observe that excluding the $1 billion termination fee payment, free cash flow grew $400 million or approximately 15% from $2.6 billion in 2020.
Our outlook for free cash flow growth in 2022 and beyond remains strong. Given this outlook, we expect share repurchases to continue to remain our highest return on capital opportunity for capital allocation, as we believe we are significantly undervalued in the market today, highlighted by the approximately $2 billion of share repurchase in the quarter and $3.5 billion of share repurchase in 2021.
Over the last decade, we've repurchased over a third of our total shares outstanding on a net basis. In 2022, we expect to return to more normalized levels of capex as we invest in technology and smart working. We expected investment of $180 million to $200 million. As we've said before, we managed capex like all of our investments on a disciplined return on capital basis. We also expect to invest organically and inorganically in content and capabilities to address unmet client needs.
Our M&A pipeline is focused on our highest priority areas, that will bring scalable solutions to our clients' growing and evolving challenges. We continue to assess all capital allocation decisions and manage our portfolio on a return on capital basis. We ended 2021, with return on capital of 27.4%, an increase of more than 1,500 basis points over the last decade.
Turning now to our balance sheet and debt capacity, we remain confident in the strength of our balance sheet and managed liquidity risk through a well-lettered debt maturity profile. In addition, we issued $500 million of senior notes in Q4. As we said before, growth in EBITDA combined with improvements in our year-end pension and lease liability balances increases the capacity we have to issue incremental debt, while maintaining our current investment grade credit ratings.
Our net unfunded from the pension balance improved by nearly $500 million in 2021, reflecting continued progress and the results of the steps we've taken over the last decade to derisk this liability and reduce volatility. This reduction in volatility is significant for many of our clients, who still have pension obligations on their balance sheets. Current market conditions and funding status are giving many clients to a chance to reduce the risk of future volatility related to funding status or regulatory changes.
Our climate change insight and analytics in this space can help our clients access new capital to efficiently reduce their risk often with the partial pension risk transfer, creating long-term opportunity for us to help our clients manage their balance sheet risk effectively.
In summary, 2021 was another year of strong top and bottom line performance, driven by the strength of our Aon United Strategy and Aon Business Services. We've attained nearly 4 billion shareholders through share repurchase and dividends in 2021. The success we achieved this year provides continued momentum as we head into 2022. We believe our disciplined approach to return on invested capital, combined with expected long-term free cash flow growth will unlock substantial shareholder value creation over the long-term.
With that, I'll turn the call back over to the operator and we'd be delighted to take your questions.