Our Annual General Meeting was held on 6 April following the publication of our 2017 financial statements, the results of which were approved in addition to our annual report. These were prepared in accordance with the latest iteration of International Financial Reporting Standards, otherwise known as IFRS, and have been audited. All the resolutions proposed prior to the congress were passed unanimously, including the re-election of the board of directors, and motions to reappoint our independent auditor and to retain the existing composition of our audit committee. Foremost, our leadership can report a positive financial performance for the twelve-month period, although as per the past four years, there will not be a dividend paid for last year. This is to facilitate our ongoing investment strategy, which has significant capital requirements, and will ensure all projects are completed on schedule.
Overall, at the end of the 2017 financial year, Rusneftegaz can report a significant 25,4% increase in pre-tax profit from $178,2 million to $223,4 million. Such accruals are largely attributable to a substantial 13,9% rise in our revenue, from $441,0 million in 2016 to $502,3 million in 2017. Material growth is recorded in all our operations, with turnover rising in our petroleum division by 27,9% and in our electricity division by 5,9%. Such results are due to an upsurge in our levels of production and rises in commodity prices during the period, offsetting the increased costs of business during the year, which rose 6,1% from $263,4 million to $279,5 million. One of the main factors leading to the production increase is our investments made in infrastructure upgrades during the past three years, with our company financing an additional $179,4 million of assets during 2017.
Of our reported revenues during the period, $206,0 million was accredited to our petroleum operations, an increase of $44,9 million year-on-year, with the remaining $296,4 million associated with the electricity division of our organization, an increase of $16,5 million from $279,9 million from 2016. Moreover, $89,8 million of the operating profit we made during 2017 was a result of our petroleum sales, with the remaining $143,3 million accredited to electricity contracts. Likewise, a total of 54,8% of the total costs we recorded, or $153,1 million, were accountable to electricity generation and 41,6%, or $116,2 million, ascribed to our petroleum production. The remaining 3,7%, or $10,2 million, is derived from head office and other unallocated expenses. Accordingly, our investments in property, plant and equipment are also split between $19,4 million of new oil and gas equipment, $159,8 million of electricity infrastructure, and a further $0,2 million of assets being purchased in unallocated sectors.
During the period, Rusneftegaz reported an increase in costs of goods sold of 6,5% from $235,6 million in 2016 to $251,0 million in 2017. The causation of the rise is attributed to escalating mineral extraction tax payments, the total of which rose 99,5% during the period from $21,8 million to $43,6 million, or from 857 rubles per barrel with certain exemptions to 919 rubles per barrel. Moreover, it can also be referenced to the 16,4% increase in depreciation, depletion and amortization recorded during the period, which escalated from $45,7 million to $53,1 million. However, both rises are considered an indirect consequence of our operations and investments, with petroleum tax rises being constituent with operating in this industry, whilst depreciation, depletion and amortization have risen proportionately to the investments we made in assets during previous years.
Such investments can be attributed to our improved production rates, with our total annual electricity output increasing by 5,0% from 10,0 TWh to 10,5 TWh. Higher rates of depletion, which increased by 1,8% from $16,7 million to $17,0 million, can also be accounted for due to increased oil production for the year, which totaled 6,16 million barrels. This is a rise of 4,8% from 6,03 million barrels in the prior year, with our average daily production also ascending from 17.747 in 2016 to 17.789 in 2017. In the last financial year, all the electricity and petroleum we produced was generated, extracted and sold to customers in the Russian Federation, whereas in 2016 whilst all electricity and petroleum was generated and or extracted domestically, $10,9 million of all our revenue was earned from foreign sales. As a result, no export duties were paid during 2017, compared to $2,3 million in 2016.
As well as export duties, the majority of our reported costs also fell during the period. The increase in the effectualness of our assets, due to investments made in the previous three years, has resulted in a 52,8% year-on-year fall in maintenance costs and a 22,6% decline in impairment compared to 2016. In our electricity division, the $274,5 million investment made last year has resulted in a reduction in fuel and water used, thus saving us $3,5 million and $0,3 million respectively, despite commodity price rises. Our management has also been able to conserve on rents, with a 29,0% fall year-on-year, and on our labor costs, which declined 1,3% from 2016. Overall, our organization amassed a cumulative $14,1 million in efficiency savings to offset the rises in our other expenses.
Likewise, during the period, our operating expenses fell by 6,6% from $10,3 million to $9,6 million, despite a 20,3% rise in our transportation costs and an increase of 21,4% in our transmission costs. Our total administrative expenses also declined by 3,5% from $9,3 million to $9,0 million, largely due to a 22,6% fall in professional fees, and declines in insurance and head office maintenance costs. Rusneftegaz did, however, report an uplift in salaries paid, rising by 4,5% from $5,4 million to $5,6 million, which can be attributed to annual pay rises for long-term personnel in January 2017. As well as expenses, our company also reported income from accrued interest, which increased net of interest expense by 7,6% year-on-year to $0,5 million, and also from our derivatives, which rose by 81,2% year-on-year to $0,1 million respectively. Financial instruments pertaining from derivative contracts, such as foreign currency forward contracts and commodity price swaps, are now valued at $0,9 million in our statement of financial position, an increase from $0,8 million in 2016.
As well as financial instruments, the value of all our non-current assets increased during 2017, including intangibles which rose in value by 2,1% to $0,1 million. This growth was due to currency conversion differences rather than any investments made during the period, whereas rises in the value of our property, plant and equipment from $987,7 million to $1,15 billion can be mostly attributed to expenditure on assets, with currency conversion differences and revaluation being secondary factors. Aggregated, this has led to a 16,5% inflation in the value of our property, plant and equipment, with $32,3 million of currency conversion differences being reported in our consolidated financial statements, a change from $179,4 million in 2016, including a foreign exchange expense of $10,0 million, up 22,5% from $8,2 million in the prior period.
Rusneftegaz also maintains control over current assets worth $113,4 million, rising 17,5% from $96,4 million in 2016, including $24,5 million of inventories, $20,5 million of receivables and $5,5 million of assets-held-for-sale. This is comparable to the $15,5 million of inventories and $10,2 million of receivables we reported in 2016, with $5,5 million of our assets-held-for-sale remaining unchanged. To continue, our organization also reported a total of $62,8 million in cash and cash equivalents, a fall of 3,7% from $65,3 million, on the reporting date. During the financial year, our company also reported a total cash flow from operating activities of $214,4 million, a fall of 5,9% to $227,9 million.
For earnings attained during 2017, Rusneftegaz accumulated an income tax bill of $48,1 million, compared to $38,6 million in the previous year. The income tax rate charged remained unchanged at 20,0% and is not expected to be adjusted in 2018, although this comparatively corresponds with 9,6% of all revenue earned during the period, up from 8,7% in 2016. This incongruity is attributable to differences in reporting between IFRS and tax laws, and thus deferred tax assets of $0,2 million and deferred tax liabilities of $20,7 million are recorded in lieu of the disparities between depreciation reported in the consolidated financial statements and in our tax returns. Correspondingly, Rusneftegaz also reported $0,2 million of deferred tax assets and deferred tax liabilities of $18,9 million in 2016. Furthermore, we also paid other taxes of $4,9 million, which are classified as taxes that are not income tax, mineral extraction tax or export duty, a rise from $4,2 million in 2016, albeit other taxes are recognized as a component of our cost of goods sold rather than as a constituent of income tax.
Presently, Rusneftegaz foresees the majority of its future growth deriving from electricity production, and thus forecasts strong revenues in our electricity generation division. This is largely as a result of the investments we made during previous years, and thus our company intends to concentrate on investing funds in increasing revenue accordingly. Likewise, the current policy of maximizing the investment of our earnings into useful assets is to be continued into 2018, as such policies have and will continue to result in greater profits in the future, although adequate levels of liquid cash will still be maintained. However, due to the continuing volatility in commodity prices and the political actions against both the Russian Federation and the oil and gas industry, there is a degree of uncertainty in petroleum revenue forecasts. Earnings from our hydrocarbon division are also expected to increase exponentially with a potential stabilization in the price of petroleum, and new efficiency measures deployed by our organization.