notes to the consolidated financial statements union pacific corporation and subsidiary companies for purposes of this report , unless the context otherwise requires , all references herein to the 201ccorporation 201d , 201ccompany 201d , 201cupc 201d , 201cwe 201d , 201cus 201d , and 201cour 201d mean union pacific corporation and its subsidiaries , including union pacific railroad company , which will be separately referred to herein as 201cuprr 201d or the 201crailroad 201d . 1 . nature of operations operations and segmentation 2013 we are a class i railroad operating in the u.s . our network includes 32070 route miles , linking pacific coast and gulf coast ports with the midwest and eastern u.s . gateways and providing several corridors to key mexican gateways . we own 26053 miles and operate on the remainder pursuant to trackage rights or leases . we serve the western two-thirds of the country and maintain coordinated schedules with other rail carriers for the handling of freight to and from the atlantic coast , the pacific coast , the southeast , the southwest , canada , and mexico . export and import traffic is moved through gulf coast and pacific coast ports and across the mexican and canadian borders . the railroad , along with its subsidiaries and rail affiliates , is our one reportable operating segment . although we provide and analyze revenue by commodity group , we treat the financial results of the railroad as one segment due to the integrated nature of our rail network . the following table provides freight revenue by commodity group: .
what percentage of total operating revenues from 2014-2016 is the revenue from coal?
although our revenues are principally derived from customers domiciled in the u.s. , the ultimate points of origination or destination for some products we transport are outside the u.s . each of our commodity groups includes revenue from shipments to and from mexico . included in the above table are freight revenues from our mexico business which amounted to $ 2.2 billion in 2016 , $ 2.2 billion in 2015 , and $ 2.3 billion in 2014 . basis of presentation 2013 the consolidated financial statements are presented in accordance with accounting principles generally accepted in the u.s . ( gaap ) as codified in the financial accounting standards board ( fasb ) accounting standards codification ( asc ) . 2 . significant accounting policies principles of consolidation 2013 the consolidated financial statements include the accounts of union pacific corporation and all of its subsidiaries . investments in affiliated companies ( 20% ( 20 % ) to 50% ( 50 % ) owned ) are accounted for using the equity method of accounting . all intercompany transactions are eliminated . we currently have no less than majority-owned investments that require consolidation under variable interest entity requirements . cash and cash equivalents 2013 cash equivalents consist of investments with original maturities of three months or less . accounts receivable 2013 accounts receivable includes receivables reduced by an allowance for doubtful accounts . the allowance is based upon historical losses , credit worthiness of customers , and current economic conditions . receivables not expected to be collected in one year and the associated allowances are classified as other assets in our consolidated statements of financial position. .