NINE MONTHS ENDED SEPTEMBER 30, 2019 COMPARED TO NINE MONTHS ENDED SEPTEMBER 30, 2018
Revenues. Revenues of $986.4 million for the nine months ended September 30, 2019 decreased 26.6 percent compared to the nine months ended September 30, 2018. Domestic revenues of $933.6 million decreased 27.0 percent for the nine months ended September 30, 2019 compared to the same period in the prior year. The decrease in revenues was due primarily to lower pricing, lower activity levels, and an unfavorable materials mix within pressure pumping, which is RPC’s largest service line. International revenues of $52.8 million decreased 19.5 percent for the nine months ended September 30, 2019 compared to the same period in the prior year. Our international revenues are impacted by the timing of project initiations and their ultimate duration and can be difficult to predict.
During the nine months ended September 30, 2019, the average price of natural gas was 12.0 percent lower and the average price of oil was 14.9 percent lower both as compared to the same period in the prior year. The average domestic rig count during the nine months ended September 30, 2019 was 14.9 percent higher than the same period in 2018.
The Technical Services segment revenues for the nine months ended September 30, 2019 decreased 28.2 percent compared to the same period in the prior year due to lower pricing and activity levels within most of the service lines which comprise this segment. The Support Services segment revenues for the nine months ended September 30, 2019 increased by 10.6 percent compared to the same period in the prior year. This increase was due principally to improved activity levels across most of the services lines within this segment. Technical Services reported an operating loss of $15.8 million during the nine months ended September 30, 2019 compared to operating profit of $196.8 million in the same period of the prior year due to lower pricing and activity levels. Support Services reported higher operating profit of $8.8 million for the nine months ended September 30, 2019 compared to $2.1 million for the nine months ended September 30, 2018.
Cost of revenues. Cost of revenues decreased 18.3 percent to $742.7 million for the nine months ended September 30, 2019 compared to $908.6 million for the nine months ended September 30, 2018. Cost of revenues decreased, consistent with lower activity levels, due to lower materials and supplies expenses within RPC’s pressure pumping service line, as well as lower fuel costs and maintenance and repairs expense. As a percentage of revenues, cost of revenues increased in the nine months ended September 30, 2019 compared to the same period in the prior year, due to lower revenues, increasingly competitive pricing for our services, and labor cost inefficiencies.
Selling, general and administrative expenses. Selling, general and administrative expenses were $131.3 million for the nine months ended September 30, 2019 and $128.1 million for the nine months ended September 30, 2018. As a percentage of revenues, these costs increased to 13.3 percent in the nine months ended September 30, 2019 compared to 9.5 percent in the nine months ended September 30, 2018 due to the leverage of lower revenues over primarily fixed expenses.
Depreciation and amortization. Depreciation and amortization increased 7.9 percent to $130.1 million for the nine months ended September 30, 2019, compared to $120.6 million for the year ended September 30, 2018 due to capital expenditures made during the previous four quarters.
Impairment and other charge. Impairment and other charges. Impairment and other charges were $71.7 million for the nine months ended September 30, 2019, primarily related to abandoning assets, retiring old equipment and personel severance costs. There were no impairment charges recorded for the nine months ended September 30, 2018. See Note 4 of the notes to the consolidated financial statements for further discussion on these charges.
Gain on disposition of assets, net. Gain on disposition of assets, net decreased to $2.9 million for the nine months ended September 30, 2019 compared to $3.5 million for the nine months ended September 30, 2018. The gain on disposition of assets, net is generally comprised of gains and losses related to various property and equipment dispositions or sales to customers of lost or damaged rental equipment.
Other (expense) income, net. Other expense, net was $0.5 million for the nine months ended September 30, 2019 compared to other income, net of $9.8 million for the same period in the prior year. Other income recorded in the nine months ended September 30, 2018 included property insurance proceeds of approximately $9.6 million.
Interest expense. Interest expense was $261 thousand for the nine months ended September 30, 2019 compared to $368 thousand for the nine months ended September 30, 2018. Interest expense consists of facility fees on the unused portion of the credit facility and the amortization of loan costs.