Total company adjusted EBITDA increased 4% to $1.324 billion and EBITDA margin expanded by 150 basis points.
Cash generation continued to be strong with operating cash flows increasing by 9% to $1.1 billion.
And finally, one of our principal measures, return on invested capital improved by 40 basis points to 14.3%.
These results were particularly noteworthy considering our annual aggregates volume declined by 3% as compared to 2019.
Aggregates pricing improved by just over 3% on both a reported and mix-adjusted basis.
Our total cost of sales per ton increased by 2%, while our unit cash cost of sales, which is more controllable, only grew by 1%.
This led to a 5.5% gain in our aggregates cash gross profit per ton.
At $7.11, we are making good progress toward our longer term goal of $9 per ton.
Collectively, gross profit improved 12% across these three segments.
Asphalt gross profit increased $12 million or 19% over the prior year, even though volumes declined 7%.
Our ready-mix concrete unit profitability increased 8%.
Average selling prices increased by 2% and volume declined by 5%, primarily as a result of the cement shortages in California.
These projects are typically more aggregate intensive, and 90% of the near-term growth in this sector will occur in Vulcan-served states according to Dodge.
That said, we expect our adjusted EBITDA to be between $1.34 billion and $1.44 billion.
We anticipate 2021 aggregates shipments could follow a range of a 2% decline to a 2% increase as compared to 2020.
We expect aggregates freight-adjusted average selling prices to increase by 2% to 4% in 2021.
We expect to further leverage our overhead costs in 2021 and anticipate our SG&A expenses to be between $365 million and $375 million.
We anticipate interest expense to approximate $130 million for the full year.
Barring any changes to federal tax law, our effective tax rate will be about 21%.
The category of depreciation, depletion, accretion and amortization expenses will be around $400 million.
Now with respect to capital expenditures, we invested $361 million in 2020.
We expect to spend between $450 million and $475 million 2021.
Adjusted EBITDA was $311 million, up 4% from last year's fourth quarter.
Aggregates volume declined by 1%, while reported pricing increased by 3% and mix adjusted pricing by 2%.
First, we recorded a one-time non-cash pension settlement charge of $23 million or $0.13 per diluted share in connection with the voluntary lump sum distribution of benefits to certain fully vested plan participants.
The resulting earnings per share effect was $0.04 per diluted share in the fourth quarter and $0.18 per diluted share for the full year.
Moving on to the balance sheet, our financial position remains very strong with a weighted average debt maturity of 13 years and a weighted average interest rate of 4%.
Our net debt to EBITDA leverage ratio was 1.6 times as of December 31, reflecting $1.2 billion of cash on hand.
Approximately $500 million of this cash will be used to repay a debt maturity coming due next month.
We returned $206 million to shareholders through increased dividends and share repurchases.
Our capital allocation priorities, which have helped to drive an improvement of 220 basis points and our return on invested capital over the last three years, remain unchanged.

Summary:
Our total cost of sales per ton increased by 2%, while our unit cash cost of sales, which is more controllable, only grew by 1%.
Average selling prices increased by 2% and volume declined by 5%, primarily as a result of the cement shortages in California.
We anticipate 2021 aggregates shipments could follow a range of a 2% decline to a 2% increase as compared to 2020.
We expect aggregates freight-adjusted average selling prices to increase by 2% to 4% in 2021.
We expect to spend between $450 million and $475 million 2021.
Aggregates volume declined by 1%, while reported pricing increased by 3% and mix adjusted pricing by 2%.