General and administrative expense. General and administrative expense (excluding equity-based compensation expense) increased from $31 million for the three months ended March 31, 2022 to $44 million for the three months ended March 31, 2023, an increase of $13 million, or 43%, primarily due to higher salary and wage expense, professional service fees, office operating costs and software license costs between periods. We had 521 and 599 employees as of three months ended March 31, 2022 and 2023, respectively. General and administrative expense on a per unit basis (excluding equity-based compensation) increased from $0.11 per Mcfe for the three months ended March 31, 2022 to $0.15 per Mcfe for the three months ended March 31, 2023 as a result of our higher overall general and administrative costs, partially offset by increased production volumes between periods.
Equity-based compensation expense. Noncash equity-based compensation expense increased from $5 million for the three months ended March 31, 2022 to $13 million for the three months ended March 31, 2023, an increase of $8 million, primarily due to an increase in the annual equity awards granted during the fourth quarter of 2022 and first quarter of 2023 as compared to prior years, which were temporarily and significantly reduced during 2020 and supplemented by our cash awards program. Our equity awards vest over three or four year service periods, and our equity incentive program began returning to normal levels in 2021. See Note 9—Equity Based Compensation and Cash Awards to the unaudited condensed consolidated financial statements for more information on equity-based compensation awards.
Depletion, depreciation and amortization expense (“DD&A expense”). DD&A expense remained relatively consistent at $168 million, or $0.60 per Mcfe, and $168 million, or $0.57 per Mcfe, for the three months ended March 31, 2022 and 2023, respectively. This decrease in DD&A expense per Mcfe between periods was primarily due to higher reserve volumes during the three months ended March 31, 2023.
Impairment of oil and gas properties. Impairment of oil and gas properties decreased from $22 million for the three months ended March 31, 2022 to $16 million for the three months ended March 31, 2023, a decrease of $6 million, or 31%, primarily related to lower impairments of expiring leases between periods. During both periods, we recognized impairments primarily related to expiring leases as well as design and initial costs related to pads we no longer plan to place into service.
Marketing Segment
Where feasible, we purchase and sell third-party natural gas and NGLs and market our excess firm transportation capacity, or engage third parties to conduct these activities on our behalf, in order to optimize the revenues from these transportation agreements. We have entered into long-term firm transportation agreements for a significant portion of our current and expected future production in order to secure guaranteed capacity to favorable markets.
Net marketing expense (calculated as marketing revenues less marketing expense) decreased from $30 million, or $0.10 per Mcfe, for the three months ended March 31, 2022 to $23 million, or $0.08 per Mcfe, for the three months ended March 31, 2023, primarily due to lower firm transportation commitments between periods.
Marketing revenue. Marketing revenue decreased from $69 million for the three months ended March 31, 2022 to $59 million for the three months ended March 31, 2023, a decrease of $10 million, or 15%, primarily due to decreased commodity prices and ethane marketing volumes between periods, partially offset by higher natural gas and oil marketing volumes. Lower ethane marketing volumes accounted for a $13 million decrease in year-over-year marketing revenues (calculated as the change in year-to-year volumes times the prior year average price), partially offset by increased oil marketing revenues of $3 million. Higher oil marketing volumes accounted for a $8 million increase in year-over-year marketing revenues (calculated as the change in year-to-year volumes times the prior year average price), and lower oil prices accounted for an approximate $5 million decrease in year-over-year marketing revenues (calculated as the change in the year-to-year average price times current year marketing volumes). Natural gas marketing revenue remained relatively consistent between periods with higher marketing volumes during the three months ended March 31, 2023 being fully offset by lower commodity prices during the same period.
Marketing expense. Marketing expense decreased from $99 million for the three months ended March 31, 2022 to $81 million for the three months ended March 31, 2023, a decrease of $18 million, or 18%. Marketing expense includes the cost of third-party purchased natural gas, NGLs and oil as well as firm transportation costs, including costs related to current excess firm capacity. The cost of third-party purchases decreased $6 million primarily due to lower commodity prices between periods, partially offset by higher natural gas and oil marketing volumes. Firm transportation costs were $32 million for the three months ended March 31, 2022 and $20 million for the three months ended March 31, 2023, a decrease of $12 million due to the reduction in firm transportation commitments and higher third-party marketed volumes between periods.
Contract termination expense. Our marketing segment did not incur any contract termination expense for the three months ended March 31, 2022. Contract termination expense attributable to our marketing segment for the three months ended