Mike Zechmeister
Chief Financial Officer at C.H. Robinson Worldwide
Thanks, Arun, and good morning, everyone.
As Bob mentioned, Q4 was another solid quarter of year-over-year growth and record annual financial results as we continue to execute on our tech plus strategy. Our total company revenue increased 43% over Q4 last year. And our adjusted gross profit or AGP was up 34%, reaching another record high at $856 million. AGP increased across each of our segments on a year-over-year basis and compared to the pre-pandemic quarter of Q4 2019.
Note that Q4 of 2021 had one less business day than Q4 of 2020 and 2019. On a per day basis, Q4 total company AGP improved by 3% sequentially, 36% year-over-year and 50% over the pre-pandemic quarter of Q4 2019. The AGP increases year-over-year were driven by both higher volumes and higher AGP per shipment in ocean, truckload and air as we pursued profitable market share gains. On a monthly basis compared to 2020, our total company AGP per business day was up 44% in October, up 32% in November and up 31% in December. For the sixth consecutive quarter, prices and costs rose across our North American truckload business. And for the fifth consecutive quarter, they reached all-time highs.
In October and November, cost per mile and price per mile were relatively flat sequentially before rising in December due to increases in load-to-truck ratios and average route guide depth. Our NAST team navigated through this environment in Q4 by growing spot truckload volume approximately 12% year-over-year, which marked the sixth quarter in a row of double-digit spot market volume growth. We also grew our Q4 contractual truckload volume by approximately 2% year-over-year despite the rising cost environment. We continue to manage our load acceptance rates to optimize contractual volume returns.
As we do each quarter, we also repriced a portion of our contract portfolio to reflect the updated cost of purchased transportation. As we repriced the contract portfolio and captured more spot volume, our truckload AGP per mile continued to improve. Q4 marked the fifth consecutive quarter of flat to increasing AGP per mile, which remains above both our five-year and 10-year averages. Truckload AGP per shipment improved by 6% sequentially and by 15% compared to Q4 of 2020. In our LTL business, Q4 AGP per order also improved by 23.5% compared to Q4 of 2020.
AGP per mile and AGP per shipment are key metrics that we use to run our NAST business rather than AGP margin percentage, which naturally rises or falls with changing market cycle pricing. For those following AGP margin percentage, it is important to factor in that contractual price changes and lag cause changes in purchase transportation. That is, if or when the market loosens on the back side of the current cycle with greater than half of our truckload volume on fixed price contracts, we would expect to see an expansion of AGP margin percent and dollars as we typically have in past cycles. We continue to focus on overall AGP dollar growth by optimizing volume and AGP per shipment across our service offerings. With our customer-centric focus, strong team and our digital investments, we expect to drive long-term growth and efficiency into our model.
Now turning to expenses. Personnel expenses were $420 million, up 35.8% compared to Q4 of last year primarily due to higher incentive compensation costs, higher headcount and the impact of short-term pandemic-related cost reductions in Q4 of last year. On a sequential basis, Q4 personnel expenses were up 5% versus Q3, with ending headcount up 4%. Our Q4 average headcount increased 11.9% compared to Q4 of 2020. Despite the tight labor market, we were able to attract the talent we needed to support continued growth, particularly in Global Forwarding and NAST.
Looking back at 2021, in Q2, we began responding to demand that was stronger than expected by adding personnel to support the business. With annual enterprise transportation volume growth of 7.9% versus average headcount growth of 4.2%, we delivered on our goal of growing volume faster than headcount in 2021. In NAST, despite an increased level of hiring in the second half of 2021 to support our future growth expectations, we delivered a 620 basis point favorable spread in our 2021 NAST Productivity Index, which measures the difference between the year-over-year change in NAST volume compared to headcount.
Before I get into our guidance for 2022 personnel expenses, let me provide some perspective on our expectations for the year ahead. Similar to the way 2021 played out from Q2 forward, we plan to add more people to support growth opportunities across the business. We expect these additions to be weighted more heavily in the front half of 2022, but still result in growing volume at a greater rate than headcount for the full year. If growth opportunities in the market play out different than we expect, we'll adjust accordingly.
We're also prioritizing the importance of retaining our talent by increasing base compensation in line with the market in order to maintain high levels of service to our customers and carriers as we value the plus part of our tech plus strategy. In 2022, we expect a year-over-year decrease in our incentive compensation expenses to partially offset the increased headcount and wage pressures. Recall that in 2021, our enterprise performance led to significant equity vesting due to the 70% year-over-year growth in our annual earnings per share and above-target bonus and commissions payouts driven by the 63% increase in pretax income and 31% growth in AGP. Taking all these factors into account and assuming current market conditions, we expect our 2022 personnel expenses to be approximately $1.6 billion to $1.7 billion, up approximately 7% at the midpoint compared to our 2021 total of $1.54 billion.
Moving on to SG&A expenses. Q4 was approximately $149 million, up 19.6%, compared to Q4 of 2020 primarily due to higher technology-related purchase services and travel expenses. For 2022, we expect total SG&A expenses to be $550 million to $600 million compared to $526 million for 2021. The approximately 9% increase at the midpoint is primarily due to a higher level of spending on technology initiatives in travel as we expect travel spending to return to approximately half of our pre-pandemic levels. 2022 SG&A expenses are expected to include approximately $100 million of depreciation and amortization, compared to $91 million in 2021. Fourth quarter interest and other expense totaled $18.4 million, up approximately $6.4 million versus Q4 last year due primarily to the impact of currency revaluation. Q4 results included a $6.5 million loss on currency revaluation compared to a $1.1 million gain in Q4 last year.
As a reminder, these are non-cash gains and losses. Interest expense was up $1.8 million due to higher level of average debt. Our Q4 tax rate came in at 14.5%, making our 2021 annual tax rate 17.4%, which was lower than our expectations primarily due to a favorable mix of foreign earnings and US tax incentives and credits. We expect to receive less benefit from these items in 2022, resulting in an expected 2022 full year effective tax rate of 19% to 21%, assuming no meaningful changes to federal, state or international tax policy. Q4 net income was $230.1 million, up 56%, compared to Q4 of 2020 and diluted earnings per share was $1.74, up 61%.
Turning to cash flow. Q4 cash flow generated by operations was approximately $76 million, compared to $162 million in Q4 of 2020. The $86 million year-over-year decline was primarily due to a $200 million increase in net operating working capital in Q4, compared to a $92 million increase in Q4 of 2020. The Q4 2021 increase resulted from a $279 million sequential increase in accounts receivable and contract assets minus a $79 million increase in total accounts payable, compared to Q3. At some point in the cycle, when the cost of purchase transportation and subsequent pricing come down to their -- from their current all-time highs, we would expect a commensurate benefit to working capital and operating cash flow.
Accounts receivable and contract assets were up 6.7% sequentially, while total revenue was up 3.8%. The resulting 1.7-day increase in days sales outstanding or DSO was driven primarily by the mix shift associated with higher revenue growth in Global Forwarding, where our DSO runs at approximately double that of our NAST business. From a quality of receivables standpoint, our percent past due and our credit losses both improved compared to Q4 a year ago. Over the long-term, we expect AGP growth to outpace working capital growth.
Capital expenditures were $18.4 million in Q4, bringing our full year capital spending to $70.9 million. For 2022, we expect our capital expenditures to be $90 million to $100 million primarily driven by technology investments. We continue to return a significant amount of capital to shareholders, including approximately $223 million in Q4 through a combination of $154.4 million of share repurchases and $68.4 million of dividends. We've repurchased approximately 1.6 million shares at an average price of $96.90 per share in Q4.
The Board of Directors also increased our share repurchase authorization by an additional 20 million shares in December, resulting in approximately 21.6 million shares of repurchase capacity remaining at year-end. For the full year, we returned $886 million to shareholders, which equates to 105% of our 2021 net income and was up 119%, compared to 2020 when we paused our share repurchase program out of an abundance of caution due to the pandemic. In December, our Board authorized and declared a 7.8% increase to our regular quarterly cash dividend, taking it to $0.55 per share from $0.51 beginning with the quarterly dividend that was paid in January of 2022. We have now distributed uninterrupted dividends without decline for more than 20 years. Over the long-term, we remain committed to our quarterly cash dividend and opportunistic share repurchase program as important levers to enhance shareholder value.
Now on to the balance sheet highlights. At the end of Q4, our cash balance was $257 million, up $14 million, compared to Q4 of 2020. Over the long-term, we will continue to look for ways to efficiently repatriate excess cash from foreign entities with the intent of only carrying the cash needed to fund operations. We ended Q4 with $732 million of liquidity comprised of $475 million of committed funding under our credit facility, which matures in October of 2023 and our Q4 cash balance. Our debt balance at year-end was $1.92 billion, up $825 million versus Q4 last year driven primarily by increases in working capital and share repurchases. Our net debt-to-EBITDA leverage at the end of Q4 was 1.42 times compared to 1.39 times at the end of Q3.
From a capital allocation standpoint, we continue to be diligent and thoughtful about high-return investments on a risk-adjusted basis as we drive further growth and efficiencies into our model. We remain committed to disciplined capital stewardship, maintaining an investment-grade credit rating and generating sustainable long-term growth in our total shareholder returns. Overall, 2021 was a year of record financial results for Robinson. We look forward to building off of our strong foundation for long-term growth.
Thank you for listening this morning. And now, I'll turn it back over to Bob for his final comments.
