Overall, electricity demand increased 3% over last year, with coal's share of electricity generation increasing to approximately 23% for the first nine months of 2021.
During the first nine months, utility consumption of PRB coal rose approximately 30% compared to prior year.
At our other U.S. thermal operations, we are ramping up volumes next year by approximately two million tons to meet increased customer demand.
Within our seaborne thermal segment, the Wilpinjong extension and the Wambo Open-Cut JV development projects continue to advance, with over $200 million of capital invested over the past three years.
Our seaborne thermal margins benefited from price increases of 66% in the quarter compared to the prior year, and the segment is on target to deliver higher export volumes in the fourth quarter as compared to prior quarters in 2021.
In the quarter, the CMJV complex and Metropolitan delivered 36% higher volumes at 16% lower cost per ton as compared to the prior year.
To date this year, we have reduced our debt levels by approximately $250 million.
Third quarter sales were over $900 million; our highest in seven quarters, an increase by more than 30% from the prior year.
Reported revenue was $679 million, net of $238 million of unrealized mark-to-market losses.
At September 30, we had hedges on 2.9 million metric tons, the majority of which were contracted in the first half of 2021 and relate to 2.1 million metric tons of expected production at our Wambo underground mine.
These tons are expected to be mined and settled at a rate of 1.4 million tons in 2022 and 0.7 million tons in 2023.
The hedge contracts support the profitability of the mine by securing average prices of $84 per metric ton through mid-2023 and are a key ingredient of a strategy to extend the expected life of the mine.
Net loss attributable to common shareholders totaled $44 million, including recognition of the $238 million of unrealized mark-to-market losses.
We reported adjusted EBITDA of $289 million, more than double the $122 million reported in the second quarter and three times the prior year results of $95 million.
Importantly, we took further action to enhance our financial strength, retiring an additional $93 million of senior secured debt in the quarter, resulting in a net gain from early debt extinguishment of $16 million.
We also retired an additional $30 million after September 30.
That brings debt retired this year to approximately $250 million, more than 16% of debt outstanding at January 1.
In the quarter, we raised net cash proceeds of $112 million by issuing nine million shares of common stock under the at-the-market equity program.
Subsequent to September 30, we raised an additional $39 million and issued 2.8 million shares.
Outstanding shares are now approximately 126 million, and we have about five million shares remaining available under the currently approved ATM program.
At September 30, we had $587 million of cash and cash equivalents, net of $240 million of cash margin posted related to the economic coal hedges previously discussed.
The seaborne thermal segment generated EBITDA of $104 million and benefited from a $23 increase in average realized prices compared to the prior year.
Wilpinjong shipped 3.5 million tons in the quarter, including 1.6 million export tons at an average cost of $26 per ton.
Wilpinjong realized average sales price of $42, resulting in EBITDA margins of approximately 40%.
Wilpinjong recorded $56 million of adjusted EBITDA and had $145 million of cash at September 30.
The seaborne met segment generated EBITDA of $57 million with an average realized price of $120 per ton and costs of 82, resulting in 32% margins.
Third quarter met shipments were approximately 400,000 tons higher than last year due to higher production at Metropolitan and the CMJV.
Total costs for the seaborne met segment were lower by more than $15 per ton compared to prior year due to elevated costs at Shoal Creek in 2020, and this despite higher royalties on favorable exchange rates and higher fuel prices in the current quarter.
In the U.S., our mines delivered $82 million of EBITDA despite challenges with labor availability and COVID related absenteeism impacting production at several operations.
Our PRB mine shipped 22.7 million tons in the quarter at a 15% margin.
The other U.S. thermal mines shipped to combined 4.5 million tons and generated 24% EBITDA margins.
Looking ahead through the remainder of the year, we anticipate higher seaborne thermal volumes, including the three million to four million export tons, of which approximately 50% are un-priced.
The seaborne met segment is expected to ship one million to 1.5 million tons in the fourth quarter, with 75% of those tons on price.
We anticipate production at Shoal Creek to recommence in the second half of the fourth quarter, with ramp-up continuing through the first quarter of next year.
Lastly, we will continue to be disciplined, taking advantage of strong markets, controlling costs and further reducing debt.

Summary:
At our other U.S. thermal operations, we are ramping up volumes next year by approximately two million tons to meet increased customer demand.
Reported revenue was $679 million, net of $238 million of unrealized mark-to-market losses.
We anticipate production at Shoal Creek to recommence in the second half of the fourth quarter, with ramp-up continuing through the first quarter of next year.
Lastly, we will continue to be disciplined, taking advantage of strong markets, controlling costs and further reducing debt.