During the second quarter, we delivered adjusted earnings per share of $1.09, which represents a 36% increase over the prior year, expanded EBITDA margin of 110 basis points to 30.6%, and generated $1 billion of adjusted free cash flow on a year-to-date basis.
Year-to-date, we invested $567 million in acquisitions to further enhance our market position and increase free cash flow.
We expect to invest well over $600 million in acquisitions for the full year.
Year-to-date, we returned $363 million to our shareholders through dividends and share repurchases, and our Board recently approved an 8% increase in the quarterly dividend.
Retention in our small and large container business remains at historically high levels at 94%.
If you further consider all permanent units of service, retention is even higher at 95%.
Total core price was 5.2%, and average yield was 2.6%.
Second quarter volume increased 8.1% compared to the prior year, which exceeded our expectations.
Through the second quarter, we implemented tablets in approximately 40% -- 47% of our large and small container fleet.
For example, we are proud to report a 5% reduction in operational greenhouse gas emissions in 2020 compared to the prior year.
This year, we expanded and converted a landfill gas energy plant to high BTU and have 15 additional projects in the pipeline.
So far this year, we've supported more than 25 charitable efforts and neighborhood revitalization projects through financial contributions and volunteer efforts.
In recognition of our ESG performance and transparency, we were named to 3BL Media's 100 Best Corporate Citizens list for the second consecutive year.
Accordingly, we are updating full year financial guidance as follows.
Adjusted earnings per share is now expected to be in a range of $4 to $4.05, and adjusted free cash flow is now expected to be in a range of $1.45 billion to $1.475 billion.
This represents an increase of over 6% from the midpoint of the prior guidance.
Second quarter core price was 5.2%, which included open market pricing of 6.5% and restricted pricing of 3%.
The components of core price included small container of 7.9%, large container of 5.3% and residential of 5%.
Average yield was 2.6%, which increased 30 basis points from the first quarter.
Second quarter volume increased 8.1%.
While we expected second quarter to be the highest reported volume for the year, the 8.1% growth exceeded our expectations.
The components of volume included an increase in small container of 8.6%, an increase in large container of 13.7% and an increase in landfill of 12.6%.
For reference, second quarter volumes in our small and large container businesses were down less than 1% from a 2019 pre-pandemic baseline, and MSW and C&D landfill volumes were both above the pre-pandemic baseline.
Commodity prices increased to $170 per ton in the second quarter.
This compared to $101 per ton in the prior year.
Recycling processing and commodity sales contributed 100 basis points to internal growth during the second quarter.
Approximately 30% of our Environmental Solutions business is in the upstream oil and gas sector, and 70% is in the downstream petrochemical and broader industrial manufacturing sectors.
The downstream petrochemical and industrial manufacturing portion of this business grew 8% compared to the prior year.
Adjusted EBITDA margin for the second quarter was 30.6% and increased 110 basis points over the prior year.
This included 130 basis points, a 50 basis point increase from recycled commodity prices and a 70 basis point headwind from net fuel.
SG&A was 10.7% of revenue, which was flat with the prior year.
SG&A would have been approximately 10%, excluding the additional incentive compensation expenses.
Year-to-date, adjusted free cash flow was $1 billion and increased $276 million or 38% compared to the prior year.
The drivers of growth included EBITDA growth in the business, a positive contribution from a 1.5-day improvement in DSO and the timing of capital expenditures.
We received approximately 40% of our projected full year capex during the first half of the year.
During the quarter, total debt was $9 billion, and total liquidity was $2.9 billion.
Interest expense decreased $13 million due to refinancing activities completed last year, and our leverage ratio was 2.9 times.
With respect to taxes, our second quarter adjusted effective tax rate was 21.6%.
We had an equivalent tax impact of 23.7% if you include noncash charges from solar investments.
We'll expect a full year equivalent tax impact of 26%, which includes the effective tax rate and noncash solar charges.

Summary:
During the second quarter, we delivered adjusted earnings per share of $1.09, which represents a 36% increase over the prior year, expanded EBITDA margin of 110 basis points to 30.6%, and generated $1 billion of adjusted free cash flow on a year-to-date basis.
Year-to-date, we returned $363 million to our shareholders through dividends and share repurchases, and our Board recently approved an 8% increase in the quarterly dividend.
Accordingly, we are updating full year financial guidance as follows.
Adjusted earnings per share is now expected to be in a range of $4 to $4.05, and adjusted free cash flow is now expected to be in a range of $1.45 billion to $1.475 billion.
The downstream petrochemical and industrial manufacturing portion of this business grew 8% compared to the prior year.