Corporation’s results following the closing of the Transactions on March 12, 2019. Total operating expenses related to the segment increased from $189 million for the six months ended June 30, 2019 to $848 million for the six months ended June 30, 2020. The increase was primarily due to impairments by Antero Midstream Corporation of $89 million on its freshwater pipelines and equipment, and an impairment charge of $575 million on its goodwill.
Discussion of Items Not Allocated to Segments for the Six Months Ended June 30, 2019 Compared to the Six Months Ended June 30, 2020
Impairment of equity investment. At March 31, 2020, we determined that events and circumstances indicated that the carrying value of our equity method investment in Antero Midstream Corporation had experienced an other-than-temporary decline and we recorded an impairment of $611 million. The fair value of the equity method investment in Antero Midstream Corporation was based on the quoted market share price of Antero Midstream Corporation at March 31, 2020.
Interest expense. Our interest expense exclusive of interest expense related to Antero Midstream Partners’ indebtedness decreased from $109 million for the six months ended June 30, 2019 to $105 million for the six months ended June 30, 2020 primarily due to the reduction in debt as a result of our debt repurchases. Consolidated interest expense decreased from $126 million for the six months ended June 30, 2019 to $105 million for the six months ended June 30, 2020, a decrease of $21 million, or 17%. During the six months ended June 30, 2019, interest related to Antero Midstream Partners’ debt through March 12, 2019 is included consolidated interest expense. Interest expense includes approximately $5.7 million and $4.8 million of non-cash amortization of deferred financing costs for the six months ended June 30, 2019 and 2020, respectively.
Transaction expense. We incurred transaction expense of $6 million in the six months ended June 30, 2020 and did not incur comparable costs in the six months ended June 30, 2019. These expenses include legal and transaction fees associated with the sale of our overriding royalty interest and the creation of Martica. See Note 4—Conveyance of Overriding Royalty Interest to the unaudited condensed consolidated financial statements included elsewhere in this Quarterly Report on Form 10-Q for more information on this transaction.
Income tax expense/benefit. Income tax expense decreased from a deferred tax expense of $305 million and $1 million of current tax expense, with an effective tax rate of 22%, for the six months ended June 30, 2019 to a deferred tax benefit of $252 million, with an effective tax rate of 24%, for the six months ended June 30, 2020. The change was primarily a result of an increase in book income due to the Transactions and the associated deconsolidation of Antero Midstream Partners for the six months ended June 30, 2019, offset by a decrease in book income resulting from the impairment of our investment in Antero Midstream Corporation and reduced revenue due to commodity price decreases for the six months ended June 30, 2020.
Capital Resources and Liquidity
Our primary sources of liquidity have been through net cash provided by operating activities including proceeds from derivatives, borrowings under the Credit Facility, issuances of debt and equity securities, distributions/dividends from unconsolidated affiliates and proceeds from our asset sale program, including the sale of the overriding royalty interest. Our primary use of cash has been for the exploration, development, and acquisition of oil and natural gas properties. As we develop our reserves, we continually monitor what capital resources, including equity and debt financings, are available to meet our future financial obligations, planned capital expenditure activities, and liquidity requirements. Our future success in growing our proved reserves and production will be highly dependent on net cash provided by operating activities and the capital resources available to us.
During the six months ended June 30, 2020, we repurchased shares of our common stock under our share repurchase program that expired March 31, 2020. We repurchased and retired 28,193,237 common shares at a weighted average price per share of $1.54 for approximately $43 million during the six months ended June 30, 2020.
We may also seek to retire or purchase our outstanding debt securities from time to time through cash purchases, in open market purchases, privately negotiated transactions or otherwise. Any such repurchases will depend on prevailing market conditions, our liquidity requirements, contractual restrictions and other factors. During the six months ended June 30, 2020, we repurchased $619 million principal amount of debt at a 19% weighted average discount, including a portion of our 2021 notes, 2022 notes, 2023 notes and 2025 notes. We recognized a gain of approximately $120 million on the early extinguishment of the debt repurchased. These repurchases, at a discount, have resulted in a net reduction in total debt outstanding and interest expense.
As of June 30, 2020, we believe that funds from operating cash flows, distributions from unconsolidated affiliates, available borrowings under the Credit Facility, or capital market transactions will be sufficient to meet our cash requirements, including normal operating needs, debt service obligations, capital expenditures, and commitments and contingencies for at least the next 12 months.