for more information on the impact of tax reform , see note 3. as a result of the enactment of this law , “ purchased services and rents ” includes a $ 151 million benefit and “ income taxes ” includes a $ 3,331 million benefit , which added $ 3,482 million to “ net income ” and $ 12.00 to “ diluted earnings per share . ” the operating ratio was favorably impacted by 1.4 percentage points . the following table adjusts our gaap financial results to exclude the effects of tax reform ( specifically , the effects of remeasurement of net deferred tax liabilities related to the reduction of the federal tax rate from 35 % to 21 % ) . we use these non-gaap financial measures internally and believe this information provides useful supplemental information to investors to facilitate making period-to-period comparisons by excluding the effects of tax reform . while we believe that these non-gaap financial measures are useful in evaluating our business , this information should be considered as supplemental in nature and is not meant to be considered in isolation or as a substitute for the related financial information prepared in accordance with gaap . in addition , these non-gaap financial measures may not be the same as similar measures presented by other companies . k 17 reconciliation of non-gaap financial measures replace_table_token_12_th in the table below and the paragraph following , references to 2017 results and related comparisons use the adjusted , non-gaap results from the reconciliation in the table above . replace_table_token_13_th the increases in net income for both comparisons resulted from higher income from railway operations . for 2017 , a 7 % increase in revenues was partially offset by a 4 % rise in adjusted operating expenses . for 2016 , an 11 % decline in operating expenses more than offset a 6 % decrease in revenues . the higher percentage increases in diluted earnings per share compared with the percentage increases in net income for both years was largely the result of our share repurchase program . k 18 detailed results of operations railway operating revenues the following tables present a three-year comparison of revenues , volumes ( units ) , and average revenue per unit by market group . replace_table_token_14_th replace_table_token_15_th replace_table_token_16_th k 19 revenues increased $ 663 million in 2017 , following a $ 623 million decline in 2016. as reflected in the table below , the rise in 2017 was largely the result of increased volume , particularly in our coal and intermodal markets , coupled with pricing gains . the decline in 2016 reflected lower revenue per unit , the effects of reduced fuel surcharges and changes in traffic mix , which more than offset price increases , as well as lower volume , primarily driven by reductions in energy-related markets and the restructuring of our triple crown services ( tcs ) subsidiary . replace_table_token_17_th most of our contracts include negotiated fuel surcharges , typically tied to either west texas intermediate crude oil ( wti ) or on-highway diesel ( ohd ) . approximately 90 % of our revenue base is covered by these negotiated fuel surcharges , with about two-thirds tied to ohd . for both 2017 and 2016 , contracts tied to ohd accounted for about 90 % of our fuel surcharge revenue , as oil price levels were below most of our surcharge trigger points in contracts tied to wti . revenues associated with fuel surcharges totaled $ 359 million , $ 236 million , and $ 477 million in 2017 , 2016 , and 2015 , respectively . merchandise revenues increased in 2017 , but decreased in 2016 , compared with the years before . in 2017 , the growth was a result of higher average revenue per unit , driven by pricing gains . volume was relatively flat compared to the prior year , as gains in the metals and construction group were offset by declines in automotive , agriculture , and chemicals traffic . in 2016 , the effects of lower volume were offset in part by a slight increase in average revenue per unit . price increases were tempered by reduced fuel surcharge revenues and unfavorable changes in traffic mix . for 2018 , merchandise revenues are expected to increase , primarily the result of pricing gains and higher fuel surcharge revenues . chemicals revenues were modestly higher in 2017 , following a decline in 2016. the increase in 2017 was due to higher average revenue per unit , a result of favorable mix and price improvements , which outweighed declines in volume . both periods reflected fewer shipments of crude oil from the bakken oil fields , and 2017 reflected lower shipments of coal ash ; in both periods , these reductions were partially offset by more shipments of plastics . the 2016 volume decline also reflected lower chlor-alkali and rock salt traffic , the result of market consolidations and softened demand . the 2016 volume decrease was offset in part by higher average revenue per unit , due to favorable mix as increased volumes of higher-rated plastics more than offset reduced fuel surcharge revenues . for 2018 , chemicals revenues are anticipated to increase , as average revenue per unit is expected to be higher , the effect of favorable mix influenced by increased volumes of higher-rated plastics and organic chemicals , as well as , overall pricing gains . we expect carload declines of liquefied petroleum gas to be offset by gains in plastics , industrial chemicals , and crude oil . one of our chemical customers , sunbelt chlor alkali partnerships ( sunbelt ) , filed in 2011 a rate reasonableness complaint before the stb alleging that our tariff rates for transportation of regulated movements are unreasonable . story_separator_special_tag we review assumptions related to our defined benefit plans annually , and while changes are likely to occur in assumptions concerning retirement age , projected earnings , and mortality , they are not expected to have a material effect on our net pension expense or net pension liability in the future . the net pension liability is recorded at net present value using discount rates that are based on the current interest rate environment in light of the timing of expected benefit payments . we utilize analyses in which the projected annual cash flows from the pension and postretirement benefit plans are matched with yield curves based on an appropriate universe of high-quality corporate bonds . we use the results of the yield curve analyses to select the discount rates that match the payment streams of the benefits in these plans . properties and depreciation most of our assets are long-lived railway properties ( note 6 ) . as disclosed in note 1 , the primary depreciation method for our asset base is group life . see note 1 for a more detailed discussion of the assumptions and estimates in this area . depreciation expense for 2017 totaled $ 1.1 billion . our composite depreciation rates for 2017 are disclosed in note 6 ; a one-tenth percentage point increase ( or decrease ) in these rates would have resulted in a $ 40 million increase ( or decrease ) to depreciation expense . for 2017 , roadway depreciation rates ranged from 0.83 % to 29.12 % and equipment depreciation rates ranged from 1.38 % to 33 % . personal injury casualties and other claims expense , included in “ materials and other ” in the consolidated statements of income , includes our accrual for personal injury liabilities . to aid in valuing our personal injury liability and determining the amount to accrue with respect to such claims during the year , we utilize studies prepared by an independent consulting actuarial firm . the actuarial firm studies our historical patterns of reserving for claims and subsequent settlements , taking into account relevant outside influences . we adjust the liability quarterly based upon our assessment and the results of the study . our estimate is subject to inherent limitation given the difficulty of predicting future events and as such the ultimate loss sustained may vary from the estimated liability recorded . for a more detailed discussion of the assumptions and estimates in accounting for personal injury see note 16. income taxes our net deferred tax liability totaled $ 6.3 billion at december 31 , 2017 ( note 3 ) . this liability is estimated based on the expected future tax consequences of items recognized in the financial statements . after application of the k 28 federal statutory tax rate to book income , judgment is required with respect to the timing and deductibility of expenses in our income tax returns . for state income and other taxes , judgment is also required with respect to the apportionment among the various jurisdictions . a valuation allowance is recorded if we expect that it is more likely than not that deferred tax assets will not be realized . we have a $ 44 million valuation allowance on $ 366 million of deferred tax assets as of december 31 , 2017 , reflecting the expectation that almost all of these assets will be realized . see discussion of tax reform in note 3. other matters labor agreements approximately 80 % of our railroad employees are covered by collective bargaining agreements with various labor unions . pursuant to the railway labor act , these agreements remain in effect until new agreements are reached , or until the bargaining procedures mandated by the railway labor act are completed . we largely bargain nationally in concert with other major railroads , represented by the national carriers conference committee ( nccc ) . moratorium provisions in the labor agreements govern when the railroads and unions may propose changes to the agreements . beginning in late 2014 , the nccc and the various unions exchanged new proposals to begin the current round of national negotiations . the unions formed three separate bargaining coalitions and the nccc has reached agreements with 2 of these coalitions representing 10 separate unions and approximately 80 % of the unionized workforce . some of these agreements ( applicable to approximately 10 % of the unionized workforce ) are still pending ratification by the union membership while the rest have already been ratified and are now final . negotiations with the other coalition is ongoing with the assistance of mediators from the national mediation board . in accordance with the railway labor act , current agreements will remain in effect during the statutory bargaining process . separately , ns has reached agreement covering wages and work rules through 2019 with the brotherhood of locomotive engineers and trainmen ( blet ) , which represents approximately 4,600 ns engineers . market risks we manage overall exposure to fluctuations in interest rates by issuing both fixed- and floating-rate debt instruments . at december 31 , 2017 , debt subject to interest rate fluctuations totaled $ 100 million . a one-percentage point increase in interest rates would increase total annual interest expense related to all variable debt by approximately $ 1 million . we consider it unlikely that interest rate fluctuations applicable to these instruments will result in a material adverse effect on our financial position , results of operations , or liquidity . new accounting pronouncements for a detailed discussion of new accounting pronouncements , see note 1. inflation in preparing financial statements , gaap requires the use of historical cost that disregards the effects of inflation on the replacement cost of property . as a capital-intensive company , we have most of our capital invested in long-lived assets . the replacement cost of these assets , as well as the related depreciation expense , would be substantially greater

cash used in investing activities was $ 1.5 billion in 2017 , compared with $ 1.8 billion in 2016 , and $ 2.1 billion in 2015 . both year-over-year comparisons reflected lower cash outflows for property additions . a decline in corporate-owned life insurance investments additionally impacted 2017. the decrease in 2016 is also a reflection of lower proceeds from corporate-owned life insurance investments . capital spending and track and equipment statistics can be found within the “ railway property ” section of part i of this report on form 10-k. for 2018 , we expect capital spending to total $ 1.8 billion . cash used in financing activities was $ 2.0 billion in 2017 , compared with $ 1.3 billion in 2016 , and $ 693 million in 2015 . both year-over-year comparisons reflected lower debt proceeds . in 2017 , the rise was further affected by increased repurchases of common stock . contributing to the increase in 2016 were higher debt repayments , partially offset by lower repurchases of common stock . share repurchases totaled $ 1.0 billion in 2017 , $ 803 million in 2016 , and $ 1.1 billion in 2015 for the purchase and retirement of 8.2 million , 9.2 million , and 11.3 million shares , respectively . on september 26 , 2017 , our board of directors authorized the repurchase of up to an additional 50 million shares of common stock through december 31 , 2022. as of december 31 , 2017 , 56.5 million shares remain authorized for repurchase .


 Write a concise suspicious activity report of the following text delimited by triple backquotes. Return your response as a formal report which covers the key points highlighting the location,dates,entity names and account holder information in chronological order of the text.
     ```cash used in investing activities was $ 1.5 billion in 2017 , compared with $ 1.8 billion in 2016 , and $ 2.1 billion in 2015 . both year-over-year comparisons reflected lower cash outflows for property additions . a decline in corporate-owned life insurance investments additionally impacted 2017. the decrease in 2016 is also a reflection of lower proceeds from corporate-owned life insurance investments . capital spending and track and equipment statistics can be found within the “ railway property ” section of part i of this report on form 10-k. for 2018 , we expect capital spending to total $ 1.8 billion . cash used in financing activities was $ 2.0 billion in 2017 , compared with $ 1.3 billion in 2016 , and $ 693 million in 2015 . both year-over-year comparisons reflected lower debt proceeds . in 2017 , the rise was further affected by increased repurchases of common stock . contributing to the increase in 2016 were higher debt repayments , partially offset by lower repurchases of common stock . share repurchases totaled $ 1.0 billion in 2017 , $ 803 million in 2016 , and $ 1.1 billion in 2015 for the purchase and retirement of 8.2 million , 9.2 million , and 11.3 million shares , respectively . on september 26 , 2017 , our board of directors authorized the repurchase of up to an additional 50 million shares of common stock through december 31 , 2022. as of december 31 , 2017 , 56.5 million shares remain authorized for repurchase .
```    
 Suspicious Activity Report : for more information on the impact of tax reform , see note 3. as a result of the enactment of this law , “ purchased services and rents ” includes a $ 151 million benefit and “ income taxes ” includes a $ 3,331 million benefit , which added $ 3,482 million to “ net income ” and $ 12.00 to “ diluted earnings per share . ” the operating ratio was favorably impacted by 1.4 percentage points . the following table adjusts our gaap financial results to exclude the effects of tax reform ( specifically , the effects of remeasurement of net deferred tax liabilities related to the reduction of the federal tax rate from 35 % to 21 % ) . we use these non-gaap financial measures internally and believe this information provides useful supplemental information to investors to facilitate making period-to-period comparisons by excluding the effects of tax reform . while we believe that these non-gaap financial measures are useful in evaluating our business , this information should be considered as supplemental in nature and is not meant to be considered in isolation or as a substitute for the related financial information prepared in accordance with gaap . in addition , these non-gaap financial measures may not be the same as similar measures presented by other companies . k 17 reconciliation of non-gaap financial measures replace_table_token_12_th in the table below and the paragraph following , references to 2017 results and related comparisons use the adjusted , non-gaap results from the reconciliation in the table above . replace_table_token_13_th the increases in net income for both comparisons resulted from higher income from railway operations . for 2017 , a 7 % increase in revenues was partially offset by a 4 % rise in adjusted operating expenses . for 2016 , an 11 % decline in operating expenses more than offset a 6 % decrease in revenues . the higher percentage increases in diluted earnings per share compared with the percentage increases in net income for both years was largely the result of our share repurchase program . k 18 detailed results of operations railway operating revenues the following tables present a three-year comparison of revenues , volumes ( units ) , and average revenue per unit by market group . replace_table_token_14_th replace_table_token_15_th replace_table_token_16_th k 19 revenues increased $ 663 million in 2017 , following a $ 623 million decline in 2016. as reflected in the table below , the rise in 2017 was largely the result of increased volume , particularly in our coal and intermodal markets , coupled with pricing gains . the decline in 2016 reflected lower revenue per unit , the effects of reduced fuel surcharges and changes in traffic mix , which more than offset price increases , as well as lower volume , primarily driven by reductions in energy-related markets and the restructuring of our triple crown services ( tcs ) subsidiary . replace_table_token_17_th most of our contracts include negotiated fuel surcharges , typically tied to either west texas intermediate crude oil ( wti ) or on-highway diesel ( ohd ) . approximately 90 % of our revenue base is covered by these negotiated fuel surcharges , with about two-thirds tied to ohd . for both 2017 and 2016 , contracts tied to ohd accounted for about 90 % of our fuel surcharge revenue , as oil price levels were below most of our surcharge trigger points in contracts tied to wti . revenues associated with fuel surcharges totaled $ 359 million , $ 236 million , and $ 477 million in 2017 , 2016 , and 2015 , respectively . merchandise revenues increased in 2017 , but decreased in 2016 , compared with the years before . in 2017 , the growth was a result of higher average revenue per unit , driven by pricing gains . volume was relatively flat compared to the prior year , as gains in the metals and construction group were offset by declines in automotive , agriculture , and chemicals traffic . in 2016 , the effects of lower volume were offset in part by a slight increase in average revenue per unit . price increases were tempered by reduced fuel surcharge revenues and unfavorable changes in traffic mix . for 2018 , merchandise revenues are expected to increase , primarily the result of pricing gains and higher fuel surcharge revenues . chemicals revenues were modestly higher in 2017 , following a decline in 2016. the increase in 2017 was due to higher average revenue per unit , a result of favorable mix and price improvements , which outweighed declines in volume . both periods reflected fewer shipments of crude oil from the bakken oil fields , and 2017 reflected lower shipments of coal ash ; in both periods , these reductions were partially offset by more shipments of plastics . the 2016 volume decline also reflected lower chlor-alkali and rock salt traffic , the result of market consolidations and softened demand . the 2016 volume decrease was offset in part by higher average revenue per unit , due to favorable mix as increased volumes of higher-rated plastics more than offset reduced fuel surcharge revenues . for 2018 , chemicals revenues are anticipated to increase , as average revenue per unit is expected to be higher , the effect of favorable mix influenced by increased volumes of higher-rated plastics and organic chemicals , as well as , overall pricing gains . we expect carload declines of liquefied petroleum gas to be offset by gains in plastics , industrial chemicals , and crude oil . one of our chemical customers , sunbelt chlor alkali partnerships ( sunbelt ) , filed in 2011 a rate reasonableness complaint before the stb alleging that our tariff rates for transportation of regulated movements are unreasonable . story_separator_special_tag we review assumptions related to our defined benefit plans annually , and while changes are likely to occur in assumptions concerning retirement age , projected earnings , and mortality , they are not expected to have a material effect on our net pension expense or net pension liability in the future . the net pension liability is recorded at net present value using discount rates that are based on the current interest rate environment in light of the timing of expected benefit payments . we utilize analyses in which the projected annual cash flows from the pension and postretirement benefit plans are matched with yield curves based on an appropriate universe of high-quality corporate bonds . we use the results of the yield curve analyses to select the discount rates that match the payment streams of the benefits in these plans . properties and depreciation most of our assets are long-lived railway properties ( note 6 ) . as disclosed in note 1 , the primary depreciation method for our asset base is group life . see note 1 for a more detailed discussion of the assumptions and estimates in this area . depreciation expense for 2017 totaled $ 1.1 billion . our composite depreciation rates for 2017 are disclosed in note 6 ; a one-tenth percentage point increase ( or decrease ) in these rates would have resulted in a $ 40 million increase ( or decrease ) to depreciation expense . for 2017 , roadway depreciation rates ranged from 0.83 % to 29.12 % and equipment depreciation rates ranged from 1.38 % to 33 % . personal injury casualties and other claims expense , included in “ materials and other ” in the consolidated statements of income , includes our accrual for personal injury liabilities . to aid in valuing our personal injury liability and determining the amount to accrue with respect to such claims during the year , we utilize studies prepared by an independent consulting actuarial firm . the actuarial firm studies our historical patterns of reserving for claims and subsequent settlements , taking into account relevant outside influences . we adjust the liability quarterly based upon our assessment and the results of the study . our estimate is subject to inherent limitation given the difficulty of predicting future events and as such the ultimate loss sustained may vary from the estimated liability recorded . for a more detailed discussion of the assumptions and estimates in accounting for personal injury see note 16. income taxes our net deferred tax liability totaled $ 6.3 billion at december 31 , 2017 ( note 3 ) . this liability is estimated based on the expected future tax consequences of items recognized in the financial statements . after application of the k 28 federal statutory tax rate to book income , judgment is required with respect to the timing and deductibility of expenses in our income tax returns . for state income and other taxes , judgment is also required with respect to the apportionment among the various jurisdictions . a valuation allowance is recorded if we expect that it is more likely than not that deferred tax assets will not be realized . we have a $ 44 million valuation allowance on $ 366 million of deferred tax assets as of december 31 , 2017 , reflecting the expectation that almost all of these assets will be realized . see discussion of tax reform in note 3. other matters labor agreements approximately 80 % of our railroad employees are covered by collective bargaining agreements with various labor unions . pursuant to the railway labor act , these agreements remain in effect until new agreements are reached , or until the bargaining procedures mandated by the railway labor act are completed . we largely bargain nationally in concert with other major railroads , represented by the national carriers conference committee ( nccc ) . moratorium provisions in the labor agreements govern when the railroads and unions may propose changes to the agreements . beginning in late 2014 , the nccc and the various unions exchanged new proposals to begin the current round of national negotiations . the unions formed three separate bargaining coalitions and the nccc has reached agreements with 2 of these coalitions representing 10 separate unions and approximately 80 % of the unionized workforce . some of these agreements ( applicable to approximately 10 % of the unionized workforce ) are still pending ratification by the union membership while the rest have already been ratified and are now final . negotiations with the other coalition is ongoing with the assistance of mediators from the national mediation board . in accordance with the railway labor act , current agreements will remain in effect during the statutory bargaining process . separately , ns has reached agreement covering wages and work rules through 2019 with the brotherhood of locomotive engineers and trainmen ( blet ) , which represents approximately 4,600 ns engineers . market risks we manage overall exposure to fluctuations in interest rates by issuing both fixed- and floating-rate debt instruments . at december 31 , 2017 , debt subject to interest rate fluctuations totaled $ 100 million . a one-percentage point increase in interest rates would increase total annual interest expense related to all variable debt by approximately $ 1 million . we consider it unlikely that interest rate fluctuations applicable to these instruments will result in a material adverse effect on our financial position , results of operations , or liquidity . new accounting pronouncements for a detailed discussion of new accounting pronouncements , see note 1. inflation in preparing financial statements , gaap requires the use of historical cost that disregards the effects of inflation on the replacement cost of property . as a capital-intensive company , we have most of our capital invested in long-lived assets . the replacement cost of these assets , as well as the related depreciation expense , would be substantially greater

