Operating expenses, as a percentage of net operating revenues, decreased from 96.6% during the six months ended June 30, 2018 to 95.5% during the six months ended June 30, 2019. Operating expenses, excluding depreciation and amortization and impairment and (gain) loss on sale of businesses, as a percentage of net operating revenues, increased from 88.9% for the six months ended June 30, 2018 to 89.8% for the six months ended June 30, 2019. Salaries and benefits, as a percentage of net operating revenues, increased from 45.0% for the six months ended June 30, 2018 to 45.4% for the six months ended June 30, 2019. This increase in salaries and benefits, as a percentage of net operating revenues, was primarily due to higher benefits expenses, including health insurance claims cost and an increase in certainnon-qualified benefit plan liabilities from overall market appreciation of plan investments. Supplies, as a percentage of net operating revenues, decreased from 16.7% for the six months ended June 30, 2018 to 16.4% for the six months ended June 30, 2019. Other operating expenses, as a percentage of net operating revenues, increased from 24.7% for the six months ended June 30, 2018 to 25.5% for the six months ended June 30, 2019. This increase in other operating expenses, as a percentage of net operating revenues, was primarily due to the change in estimate for professional liability claims expense and the bad debt expense for the reserve recorded for a promissory note from the buyer of two of our former hospitals in 2017 that filed for bankruptcy as described above. Expense related to government and other legal settlements and related costs, as a percentage of net operating revenues, remained consistent at 0.1% for both of thesix-month periods ended June 30, 2019 and 2018. Lease cost and rent, as a percentage of net operating revenues, remained consistent at 2.4% for both of thesix-month periods ended June 30, 2019 and 2018.
Depreciation and amortization, as a percentage of net operating revenues, decreased from 4.9% for the six months ended June 30, 2018 to 4.6% for the six months ended June 30, 2019, primarily due to ceasing depreciation on property and equipment at hospitals sold or held for sale.
Impairment and (gain) loss on sale of businesses was $71 million for the six months ended June 30, 2019, compared to $202 million for the six months ended June 30, 2018, related to impairment of the long-lived assets and reporting unit goodwill allocated to hospitals classified as held for sale or sold during the respective periods.
Interest expense, net, increased by $58 million to $522 million for the six months ended June 30, 2019 compared to $464 million for the six months ended June 30, 2018, which was driven by an increase in interest rates during the six months ended June 30, 2019, compared to the same period in 2018, which resulted in an increase in interest expense of $71 million. This increase was partially offset by a decrease in our average outstanding debt during the six months ended June 30, 2019, which resulted in a decrease in interest expense of $11 million, and an increase in major construction projects during the six months ended June 30, 2019 resulted in $2 million more interest being capitalized, compared to the same period in 2018.
Loss from early extinguishment of debt of $31 million was recognized during the six months ended June 30, 2019, as a result of the Credit Facility amendment and repayment of the term loans under the Credit Facility as discussed further in Capital Resources. Gain from early extinguishment of debt of $59 million was recognized during the six months ended June 30, 2018 which resulted primarily from the refinancing and exchange of certain of our outstanding notes and repayment of a portion of our term loans under the Credit Facility as discussed further in Capital Resources.
Equity in earnings of unconsolidated affiliates, as a percentage of net operating revenues, remained consistent at 0.2% for both of thesix-month periods ended June 30, 2019 and 2018.
The net results of the above-mentioned changes resulted in loss before income taxes increasing $100 million from $143 million for the six months ended June 30, 2018 to $243 million for the six months ended June 30, 2019.
Our provision for income taxes for the six months ended June 30, 2019 was $3 million compared to a benefit from income taxes of $45 million for the six months ended June 30, 2018. Our effective tax rates were (1.2)% and 31.5% for the six months ended June 30, 2019 and 2018, respectively. The difference in our effective tax rate for the six months ended June 30, 2019, when compared to the six months ended June 30, 2018, was primarily due to an increase in the valuation allowance recognized on IRC Section 163(j) interest carryforwards and the write-off of non-deductible goodwill.
Net loss, as a percentage of net operating revenues, increased from (1.4)% for the six months ended June 30, 2018 to (3.7)% for the six months ended June 30, 2019.
Net income attributable to noncontrolling interests, as a percentage of net operating revenues, increased from 0.5% for the six months ended June 30, 2018 to 0.6% for the six months ended June 30, 2019.
Net loss attributable to Community Health Systems, Inc. was $285 million for the six months ended June 30, 2019, compared to $135 million for the six months ended June 30, 2018.
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