Michael Zechmeister
Analyst · Chris Wetherbee with Citi
Thanks, Bob, and good afternoon, everyone. As Bob mentioned, we delivered another quarter of record financial results in Q3, driven by strong performance in a favorable market as we continue to execute on our tech plus strategy.
Our total company revenue increased 48% over Q3 last year, and our adjusted gross profit, or AGP, was up 43%. Increased AGP was driven by both volume and AGP per shipment across ocean, air, truckload and LTL. Total company AGP also improved by 13% sequentially and 33% over the pre-pandemic quarter of Q3 2019.
On a monthly basis compared to 2020, our total company AGP per business day improved in each sequential month of the quarter and was up 51% in July, up 39% in August and up 40% in September. For the fifth consecutive quarter, prices and costs rose across our North American truckload business with cost per mile and price per mile each reaching new highs in each month of Q3 due to the persisting supply-demand imbalance. Our NAST team navigated through this environment by continuing to grow spot volume, which was up approximately 14% year-over-year in Q3, marking the fifth quarter of double-digit spot market volume growth.
Within our contractual freight business, where Q3 volume was flat, we continued to selectively reprice the portfolio to reflect the ever-increasing cost of purchased transportation in this market. As Bob mentioned, our Q3 truckload AGP per mile is now above both our 5-year and 10-year averages. AGP per mile and AGP per load are key metrics in our truckload business rather than an AGP margin percentage, which naturally rises or falls with the changing market cycle pricing. For those following AGP margin percentage, if or when the market loosens within the current cycle, with the greater than 2/3 of our truckload volume on 12-month contracts, we would expect to see AGP margin percent expansion as we typically have in the past.
We continue to focus on overall AGP dollar growth by optimizing volume and AGP per shipment across our service offerings. With enhanced customer focus and digital investments, we expect to drive long-term growth and efficiency into our model.
Now turning to expenses. Q3 personnel expenses were $399.9 million, up 32% compared to Q3 of last year, primarily due to higher incentive compensation costs and the impact of short-term pandemic-related cost reductions in Q3 of last year. Our Q3 average headcount increased 7.1% compared to Q3 last year. Despite the tight labor market, we successfully hired the talent we need to support our growth expectations, particularly in Global Forwarding and NAST.
Given the increase in incentive compensation resulting from our profit expectations for 2021 and the additional headcount, we now expect 2021 personnel expenses to be in the $1.5 billion to $1.55 billion range, which is up from our prior expectations of $1.42 billion to $1.48 billion.
Q3 SG&A expenses of $133.5 million were up 13% compared to Q3 of 2020, primarily due to the impact of short-term pandemic-related cost reductions in Q3 of last year. We continue to expect 2021 total SG&A expenses to be approximately $0.5 billion, including approximately $90 million to $95 million of depreciation and amortization.
Our Q3 income from operations was a quarterly record at $310.8 million, up 85% versus Q3 last year, and our adjusted operating margin of 36.8% was up 820 basis points compared to last year and up 510 basis points from the pre-pandemic quarter of Q3 2019.
Third quarter interest and other expense totaled $16.7 million, up approximately $9.2 million versus Q3 last year due primarily to the impact of currency revaluation. Q3 results included a $3.8 million loss on currency revaluation compared to a $3.3 million gain in Q3 last year. Interest expense was also up $1.2 million due to the higher average debt balance.
Our Q3 tax rate came in at 16.0%, our second lowest tax rate on record, which was only eclipsed by the 15.1% rate from Q3 last year. This year's Q3 rate was lower than our expectations, primarily due to the favorable mix of foreign earnings and U.S. tax incentives. We are now expecting our 2021 full year effective tax rate to be 18% to 19% compared to our prior estimate of 20% to 22%.
Q3 net income was $247.1 million, up 81% compared to Q3 last year, and diluted earnings per share was a quarterly record at $1.85, up 85% versus Q3 last year.
Turning to cash flow. Q3 cash flow used by operations was approximately $74 million compared to $169 million used in Q3 last year. Sequentially, cash flow from operations declined by $223 million, driven primarily by a $679 million sequential increase in accounts receivable and contract assets, and partially offset by a $267 million increase in total accounts payable and the $247 million in net income. In Q3, accounts receivable and contract assets were up 19.6% sequentially, while total revenue was up 13.2%. The resulting 3.9 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 approximately double that of our NAST business.
While our accounts receivable balance has grown, we are not seeing quality issues as our percentage past due and credit losses have both improved compared to our 3-year averages. Over the long term, we expect AGP growth to outpace working capital growth. Capital expenditures were $22.7 million in Q3, up from $15.2 million in Q3 last year. We now expect our technology-driven 2021 capital expenditures to be $70 million to $80 million, up from our previous expectation of $55 million to $65 million.
We returned approximately $237 million of cash to shareholders in Q3 through a combination of $168 million of share repurchases and $69 million of dividends. That level of cash returned to shareholders represents a 230% increase versus Q3 last year when we were not repurchasing shares out of an abundance of caution due to the pandemic. During Q3 this year, we repurchased approximately 1.9 million shares at an average price of $90.58. At the end of Q3, we had approximately 3.2 million shares of capacity remaining on our 15 million share repurchase authorization from May of 2018.
Our cash balance at the end of Q3 was $203 million, down $41 million compared to Q3 of 2020, and we continue to work down our cash balance through efficient repatriation of excess cash from foreign entities with the end goal of carrying only the cash we need to fund operations. We ended Q3 with $571 million of liquidity comprised of $368 million of committed funding under our credit facility, which matures in October of '23, and our Q3 cash balance. Our debt balance at quarter end was $1.73 billion, up $633 million versus Q3 last year, driven primarily by increased working capital and share repurchases.
Our net debt-to-EBITDA leverage at the end of Q3 was 1.39x, up sequentially from 1.25x at the end of Q2. From a capital allocation standpoint, we continue to be committed to disciplined capital stewardship, maintaining an investment-grade credit rating and generating sustainable long-term growth in our total shareholder returns.
Overall, our NAST team made progress towards our truckload volume growth expectations. As you saw in Q3, the percentage increase in price per mile was higher than the percent increase in cost per mile for the first time in 9 quarters. While there is no telling where the market is headed, inflections like we saw in Q3 have historically led to periods with our highest AGP margins.
The Global Forwarding team continued to generate significant earnings while building on a solid foundation for future growth. The expanded global team, with upgraded tech and more uniform operations across the globe, is now onboarding its strongest pipeline of new customers.
Thank you for listening this afternoon. And I'll turn the call back over to Bob now for his final comments.