Michael Zechmeister
Analyst
Thanks, Bob, and good morning, everyone. Our third quarter gross revenues increased 9.6% compared to Q3 last year. The increase in gross revenue was driven by both higher pricing and higher volume across the majority of our service lines.
Total company net revenues decreased 7% in the third quarter, primarily due to a 12.6% increase in the cost of purchased transportation. In NAST truckload, the increase in cost resulted in a 25% decrease in truckload net revenue per load compared to Q3 last year. As Bob mentioned, our net revenue per business day hit a low point in July and improved sequentially in both August and September.
Our monthly net revenues per business day in Q3 were down 12% in July, down 6% in August and down 3% in September compared to the same periods last year. As Bob mentioned, in October, we are seeing year-over-year growth in total company net revenue per business day, which is the first month of growth in over a year.
Q3 personnel expenses totaled $302.9 million, down 5.5% versus Q3 last year, primarily driven by our cost reduction initiatives. Average head count decreased 5.6% despite the Prime acquisition adding approximately 2 percentage points. Average full-time equivalent head count, which accounts for employees with reduced work hours, decreased 7.6% compared to Q3 last year.
Q3 SG&A expenses of $118.1 million were up 5.7% or $6.3 million compared to Q3 last year despite significant reductions in travel. The overall increase was primarily due to ongoing expenses from the Prime acquisition and Q3 last year benefiting from a $5.8 million gain on the sale of an office building in Chicago.
Overall, our short-term cost reduction efforts generated approximately $40 million of savings again in the third quarter. As we communicated previously, we put in place cost savings initiatives impacting personnel noncritical project spending, travel and entertainment and the temporary suspension of the company matched retirement plans in the U.S. and Canada. As a result of these initiatives, we estimate the short-term cost savings in 2020 will now be approximately $90 million compared to our Q1 run rate, which is up from the $80 million we communicated on the Q2 earnings call.
Total third quarter operating income was down 16.3% versus last year, and operating margin declined by approximately 310 basis points compared to Q3 last year, primarily due to the decline in net revenue dollars and partially offset by reductions in personnel expenses.
Third quarter interest and other expenses totaled $7.5 million, down $5.7 million compared to Q3 last year. Q3 interest expense declined by $0.8 million to $11.9 million compared to $12.7 million in Q3 last year due to a lower average debt balance.
Our Q3 weighted average interest rate was 4.2% compared to 4.1% in Q3 last year. Our other expenses in Q3 also included a $3.3 million gain from currency revaluation compared to a $1.1 million loss in Q3 of last year.
Our third quarter effective tax rate was 15.1%, a 670 basis point improvement compared to the 21.8% rate in Q3 last year. Our Q3 effective tax rate included discrete benefits from foreign tax credit utilization and an additional deduction from increased employee stock option activity in the quarter. We now expect our 2020 full year effective tax rate to be 18% to 20%, down from the 20% to 22% range that we communicated previously.
Net income totaled $136.5 million in the third quarter, and diluted earnings per share was $1, down 6.5% versus Q3 last year.
Turning now to cash flow. Q3 cash used by operations was approximately $169 million compared to cash generation of $167 million in Q3 last year.
The $336 million decrease was driven primarily by a $362 million sequential increase in accounts receivable and contract assets compared to Q2 this year. This 16.7% sequential increase in accounts receivable coincided with a 16.5% sequential increase in gross revenue. Despite the increase, the quality of our receivables improved in Q3 as the percent of accounts receivable that were past due improved by 60 basis points compared to Q2.
Year-to-date volatility in cash flow from operations has experienced similar volatility as our overall business, with low cash generation in Q1, high cash generation in Q2 and cash usage in Q3. While none of these quarters on their own are indicative of our ongoing expectations, I would point to a more normalized year, like 2019, where we delivered $835 million of operating cash flow as more indicative of our expectations going forward.
Q3 capital expenditures totaled $15.2 million, bringing our year-to-date capital spending to $40.3 million. We now expect our 2020 full year capital expenditures to be in the $50 million to $55 million range, down from our July communication of landing at the low end of a $60 million to $70 million range. We continue to prioritize the highest returning technology initiatives on a risk-adjusted basis, and we remain committed to our $1 billion investment in technology from 2019 to 2023.
We returned approximately $71.9 million of cash to shareholders in Q3, which consisted almost entirely of our quarterly dividend. As previously communicated, we placed a hold on our share repurchase program in March out of an abundance of caution given the uncertainties posed by the pandemic. Our plan is to resume our opportunistic share repurchase program here in the fourth quarter. Over the long term, we remain committed to our quarterly dividend and opportunistic share repurchase program as important levers to enhance shareholder value.
Now on to the balance sheet highlights. We finished Q3 with $253 million in cash and cash equivalents. Over the long term, we intend to carry only the cash needed to fund operations and to maintain a debt-to-EBITDA ratio that helps us deliver and investment-grade credit rating.
Our debt balance at quarter end was $1.15 billion, down $100 million versus Q3 last year. Our gross debt-to-EBITDA leverage at quarter end was 1.62x. We ended Q3 with a solid $1.44 billion of liquidity comprised of our cash balance, $1 billion of committed funding under our credit facility, which is undrawn and matures in October of 2023, and $190 million of available credit from our accounts receivable securitization, which matures this December.
We continue to seek out and deliver on opportunities to drive long-term efficiency and savings into our business model, primarily through process redesign and automation in our NAST and other business segments. The pandemic has driven new insights around what the new normal will look like at Robinson post pandemic. Going forward, we are evaluating the optimization of our real estate footprint across the network as we expect flexible work arrangements to become more permanent.
We also expect to see lower sustained level of travel expense as we enhance our virtual communication efforts.
Of the $100 million per year of long-term or permanent savings that we committed to by the end of 2022, we now expect to deliver 2/3 of that in 2020. Please note, that there is approximately $20 million of savings that began as short-term savings meant for 2020 only and was later converted to permanent savings as we have reconceptualized our business needs post the pandemic.
As a result, that $20 million is included in both our short-term and long-term savings totals for 2020. As Bob mentioned, we now expect to complete the full $100 million of permanent cost savings by the middle of 2021, which will be half of the 3-year time horizon that we originally communicated.
The long-term cost savings initiatives are important to our 2021 results as we expect incentive compensation to be a sizable headwind, which coincides with our expectation of a better year-over-year financial results. We continue our efforts to emerge stronger and define our new normal post pandemic. As a more capable and more efficient enterprise that is focused on profitable market share gains.
Thanks for listening this morning. And now I'll turn the call back over to Bob for his final comments.