communication, secured ample safe daily water supply, offered increased housing flexibility and relaxed field schedules to allow for individual needs. Most of our day to day operations consist of small, often times individual, isolated work groups.
While our revenues are mainly affected by the level of client demand for our services, our revenues are also affected by the pricing for our services that we negotiate with our clients and the productivity and utilization level of our data acquisition crews. Factors impacting productivity and utilization levels include: client demand, commodity prices, whether we enter into turnkey or dayrate contracts with our clients, the number and size of crews, the number of recording channels per crew, crew downtime related to inclement weather, delays in acquiring land access permits, agricultural or hunting activity, holiday schedules, short winter days, crew repositioning and equipment failure. To the extent we experience these factors, our operating results may be affected from quarter to quarter. Consequently, our efforts to negotiate more favorable contract terms in our supplemental service agreements, mitigate permit access delays and improve overall crew productivity may contribute to growth in our revenues. Further, the ongoing COVID-19 pandemic may compound one or more of the foregoing factors and could directly affect our productivity.
Results of Operations
Operating Revenues. Operating revenues for the third quarter of 2020 decreased 76.4% to $8,738,000 compared to $36,976,000 in the same period of 2019. Operating revenues decreased 31.2% to $77,216,000 during the first nine months of 2020 compared to $112,216,000 in the same period of 2019. The decreased revenue during the third quarter and first nine months of 2020 when compared to the third quarter and first nine months of 2019 is primarily due to low crew utilization during those periods of 2020.
Operating Expenses. Operating expenses for the third quarter of 2020 decreased 63.7% to $9,441,000 compared to $26,030,000 in the same period of 2019. Operating expenses decreased 36.9% to $58,189,000 during the first nine months of 2020 compared to $92,210,000 in the same period of 2019. The decrease in operating expenses was primarily due to a decreased crew count and reduced crew cost structure related to workforce reductions that occurred in the second and third quarters of 2020.
General and Administrative Expenses. General and administrative expenses were 37.4% and 14.5% of revenues in the third quarter and first nine months of 2020, respectively, compared to 10.3% and 11.9% of revenues in the same periods of 2019. General and administrative expenses decreased $527,000 or 13.9% to $3,270,000 during the third quarter of 2020 from $3,797,000 during the same period of 2019, and decreased $2,185,000 or 16.3% to $11,205,000 during the first nine months of 2020 from $13,390,000 during the same period of 2019. The primary factors for the decrease in general and administrative expenses during the third quarter and first nine months of 2020 when compared to the same periods of 2019 was due to workforce reductions, salary reductions, and continued cost reduction efforts by management during the first nine months of 2020.
Depreciation and Amortization Expense. Depreciation and amortization expense for the third quarter and first nine months of 2020 totaled $4,125,000 and $13,412,000, respectively, compared to $5,238,000 and $16,644,000 for the same periods of 2019, respectively. Depreciation expense decreased in 2020 compared to 2019 as a result of multiple years of reduced capital expenditures. Our depreciation expense is expected to remain below that of 2019 for the remainder of 2020 due to the anticipated continuation of maintenance levels of capital expenditures to maintain our existing asset base.
Total operating costs for the third quarter of 2020 were $16,836,000, representing a 52.0% decrease from the same period of 2019. The operating costs for the first nine months of 2020 were $82,806,000, representing a 32.3% decrease from the same period of 2019. This decrease was primarily due to the factors described above.
Income Taxes. Income tax expense for the third quarter and first nine months of 2020 was $15,000 and $15,000, respectively, compared to income tax benefit of $25,000 and $146,000 for the same periods of 2019. These amounts represent effective tax rates of -0.2% and -0.3% for the third quarter and first nine months of 2020, respectively, compared to -1.3% and 1.5% for the third quarter and first nine months of 2019, respectively. The Company’s effective tax rate decreased compared to the corresponding period from the prior year primarily due to a 2019 PP&E-related tax adjustment.
Our effective tax rates differ from the statutory Federal rate of 21.0% for certain items such as state and local taxes, valuation allowances, non-deductible expenses and discrete items. For further information, see Note 9 of the Notes to the Condensed Consolidated Financial Statements.