Jay Johnson
Analyst · those discussed in this call and the company's third quarter 2021 earnings release and its most recent annual report on Form 10-K. Lamar refers you to those documents.
Lamar's third quarter 2021 earnings release, which contains information required by Regulation G regarding certain non-GAAP financial measures was furnished to the SEC on Form 8-K this morning and is available on the Investors section of Lamar's website, www.lamar.com. I would now like to turn the conference over to Sean Reilly. Mr. Reilly, you may begin
Thanks, Sean. Good morning, everyone, and thank you for joining us. I will begin with brief comments on the quarter, then review our balance sheet and conclude with a discussion of our current financial position, including a little more detail around this morning's revised guidance. Once again, we are extremely pleased with our quarterly results, which exceeded internal expectations as well as consensus estimates for revenue, adjusted EBITDA and AFFO. The company achieved AFFO growth for the fourth consecutive quarter improving 43.9% to $1.90 per share on a fully diluted basis versus Q3 2020.
In the third quarter, acquisition-adjusted revenue increased 23.3% from the same period last year, demonstrating the resilience of our business and the benefits of our operating model with a portfolio heavily concentrated in billboards. Q3 acquisition-adjusted revenue and adjusted EBITDA both exceeded the third quarter of 2019. Despite our airport and transit operations recovering slower than the rest of the business, each of July, August and September improved over 2019 on the top line as well as EBITDA.
As you may recall, in response to COVID-19, we implemented several cost reduction initiatives during 2020. With the second and third quarters returning to more normal levels, acquisition adjusted operating expenses increased 14.8% in the third quarter, driven primarily by variable expenses tied to revenue. We reduced operating expenses by approximately $80 million in 2020 and anticipate about half of those expenses or $40 million would return as revenue rebound. With revenue performance exceeding our expectations from the beginning of the year, we now forecast $50 million to $55 million of operating expenses will return in 2021, with full year expenses coming in around $945 million to $950 million.
Despite this acceleration in expenses, the company still expects to maintain strong adjusted EBITDA margins for the full year. Adjusted EBITDA for the quarter was $230.7 million compared to $170.7 million in 2020, which was an increase of 35.2%. On an acquisition-adjusted basis, the increase was 33.8%. Adjusted EBITDA margin was 48.4% versus 44.2% in the third quarter of 2020 and 140 basis points ahead of the same period in 2019. The work we've done on our balance sheet continues to prove beneficial as lower interest contribute significantly to AFFO growth. Free cash flow in the quarter also improved, increasing 36.6% versus the same period last year.
We experienced another quarter of acceleration in both local and national business across our portfolio. While both were up significantly relative to the third quarter of last year, our national revenue growth outpaced local by over 2x and grew faster than local for the second consecutive quarter. Consistent with historical levels, local and regional sales accounted for 76% of billboard revenue in the third quarter, while national and programmatic represented 24%. In 2020, we demonstrated Lamar's operational flexibility on many fronts, including our disciplined approach to CapEx. This year, we have returned to a more typical capital deployment program. And during the third quarter, total CapEx was approximately $30 million with maintenance CapEx comprising $13.1 million. Total spend year-to-date is approximately $72 million, and we expect CapEx for the full year to total roughly $120 million, including $55 million of maintenance CapEx.
As discussed on our last call, volume and our acquisition pipeline accelerated beginning in late spring and continued throughout the summer. In the third quarter, we closed on $80 million of acquisitions bringing the total to $108 million year-to-date through September 30. The activity we are seeing is quite promising as 2021 should be one of our more active years on the acquisition front, and we anticipate acquisition activity will exceed $250 million for the year. However, our intent is to remain prudent as we have consistently in the past and deployed capital in an efficient manner for our shareholders.
Turning to our balance sheet, which continues to be a critical focus for the company and core to our strategy and competitive advantage. We are quite pleased with the financial strength of Lamar, and our balance sheet is well positioned going forward. As a result of our conservative capital structure and the improvement in operating performance, our credit ratings were upgraded at both Moody's and S&P during the third quarter. The rating actions were based on revenue recovery and declining leverage both evident again in the third quarter. S&P improved our rating from BB- with a negative outlook to BB flat and now with a stable outlook.
In September, Moody's upgraded Lamar's corporate family rating to Ba2 from Ba3; and also upgraded our investment-grade secured rating from Baa3 to Baa2. We are in constant dialogue with the rating agencies, and are pleased to see our focus on the balance sheet rewarded with stronger ratings from both Moody's and S&P.
We have a well-laddered debt maturity schedule with no maturities until the AR securitization in July 2024, followed by the revolving portion of our credit facility in February 2025, and we have no bond maturities until 2028. Net interest expenses totaled $24.5 million in the quarter, which is approximately $8.7 million lower than Q3 2020. Based on debt outstanding at quarter end, our weighted average interest rate was 3.3% with a weighted average debt maturity of 7.3 years. As defined under our credit facility, we ended the quarter with total leverage of 3.2x net debt to EBITDA, which is the company's lowest since the fourth quarter of 2015. Our secured debt leverage was 0.6x at quarter end, and we're comfortably in compliance with both our total debt incurrence and secured debt maintenance test against covenants of 7x and 4.5x, respectively.
At the end of the quarter, we had approximately $823 million of liquidity, comprised of $87 million of cash on hand and $736 million available under our revolver. Subsequent to quarter end, we repaid $60 million on the AR securitization and currently have $115 million outstanding. Also in the quarter, we extended our debt and share repurchase programs through March 2023. Terms and conditions remain the same, and the company may repurchase common stock and any outstanding indebtedness up to $250 million each. While we do not anticipate activity under either program in the near term, we view maintaining both programs as part of our corporate finance strategy and key to preserving financial flexibility.
As Sean mentioned, and included in this morning's release, we increased our AFFO guidance based on strong performance in the first 3 quarters of the year and the outlook for Q4. The revised AFFO guidance of $6.35 to $6.50 per share represents an increase of $0.225 at the midpoint compared to our guidance released in August. As stated on our last call, we still anticipate the second and third quarters to be this year's strongest on a comparable basis. Given the solid performance in Q4 2020, which included political in our presidential year, we expect Q4 2021 to have a more difficult comparison year-over-year. Because of our efforts around the balance sheet, cash interest in 2021 should be approximately $102 million or about $28 million lower than full year 2020.
Taxes should come in slightly lower than our historical $10 million to $11 million level due to operations in the TRS, primarily our airport and transit divisions that are recovering slower than the rest of our business. When all is said and done, we expect full year EBITDA easily to exceed 2019's total of $785 million. In addition, the low end of today's revised guidance is $0.15 above the top end of our original 2020 AFFO guidance prior to the pandemic.
Now moving to our dividend. We paid a cash dividend of $0.75 per share in each of the first and second quarters and increased the dividend 33% in Q3 to $1 per share. Management's recommendation at the upcoming Board meeting will be to declare a cash dividend of $1 per share for the fourth quarter as well. This recommendation is subject to Board approval, and we will communicate the Board's decision following the Board of Directors' meeting in December. As you may recall, in 2020, prior to the pandemic, we anticipated a dividend of $4 per share for the full year and the company's goal has been to return to that level of distribution as soon as possible. To that end, we have not ruled out recommending a special dividend to the Board that will bring our 2021 full year dividend back to the same $4 per share level anticipated in 2020 prior to the pandemic.
Again, we are extremely pleased with this quarter's performance and are optimistic about the outlook for the fourth quarter with full year results that should exceed 2019 on both EBITDA and AFFO. Our balance sheet remains strong, and we maintain excellent access to both the debt and equity capital markets. A strong balance sheet is core to our operating strategy and serves as a significant competitive advantage. With our intense focus on the company's capital structure and increased flexibility, Lamar remains well positioned to take advantage of opportunities as they arise. I will now turn the call back over to Sean.