SEGMENT INFORMATION Our reportable segments, which are the same as our operating segments, are organized based on the nature of markets and customers. We report our operating results through our four operating segments that consist of similar products and services within each segment as described below. Our operating results are reviewed regularly by the chief operating decision maker, who is our Chief Executive Officer, in deciding how to allocate resources and assess performance. OILFIELD SERVICES Oilfield Services provides products and services for onshore and offshore operations across the lifecycle of a well, ranging from drilling, evaluation, completion, production and intervention. Products and services include diamond and tri-cone drill bits, drilling services, including directional drilling technology, measurement while drilling &amp; logging while drilling, downhole completion tools and systems, wellbore intervention tools and services, wireline services, drilling and completions fluids, oilfield and industrial chemicals, pressure pumping, and artificial lift technologies, including electrical submersible pumps. OILFIELD EQUIPMENT Oilfield Equipment provides a broad portfolio of products and services required to facilitate the safe and reliable flow of hydrocarbons from the subsea wellhead to the surface. Products and services include pressure control equipment and services, subsea production systems and services, drilling equipment, and flexible pipeline systems. Oilfield Equipment designs and manufactures onshore and offshore drilling and production systems and equipment for floating production platforms and provides a full range of services related to onshore and offshore drilling activities. TURBOMACHINERY &amp; PROCESS SOLUTIONS Turbomachinery &amp; Process Solutions provides equipment and related services for mechanical-drive, compression and power-generation applications across the oil and gas industry as well as products and services to serve the downstream segments of the industry including refining, petrochemical, distributed gas, flow and process control and other industrial applications. The Turbomachinery &amp; Process Solutions portfolio includes drivers (aero-derivative gas turbines, heavy-duty gas turbines and synchronous and induction electric motors), compressors (centrifugal and axial, direct drive high speed, integrated, subsea compressors, turbo expanders and reciprocating), turn-key solutions (industrial modules and waste heat recovery), pumps, valves, and compressed natural gas (CNG) and small-scale liquefied natural gas (LNG) solutions used primarily for shale oil and gas field development. DIGITAL SOLUTIONS Digital Solutions provides equipment, software, and services for a wide range of industries, including oil &amp; gas, power generation, aerospace, metals, and transportation. The offerings include sensor-based process measurement, non-destructive testing and inspection, turbine, generator and plant controls and condition monitoring, as well as pipeline integrity solutions. SEGMENT RESULTS Summarized financial information is shown in the following tables. Consistent accounting policies have been applied by all segments within the Company, for all reporting periods. The current year results, and balances, may not be comparable to prior years as the current year includes the results of BHI from July 3, 2017. Segment revenue 2019 2018 2017 Oilfield Services $ 12,889 $ 11,617 $ 5,881 Oilfield Equipment 2,921 2,641 2,661 Turbomachinery &amp; Process Solutions 5,536 6,015 6,295 Digital Solutions 2,492 2,604 2,342 Total $ 23,838 $ 22,877 $ 17,179 The performance of our operating segments is evaluated based on segment operating income (loss), which is defined as income (loss) before income taxes and equity in loss of affiliate and before the following: net interest expense, net other non operating income, corporate expenses, restructuring, impairment and other charges, inventory impairments, separation and merger related costs, goodwill impairments and certain gains and losses not allocated to the operating segments. Segment income (loss) before income taxes 2019 2018 2017 Oilfield Services $ 917 $ 785 $ 67 Oilfield Equipment 55  26 Turbomachinery &amp; Process Solutions 719 621 665 Digital Solutions 343 390 357 Total segment 2,035 1,796 1,115 Corporate (433 ) (405 ) (370 ) Inventory impairment and related charges (1)  (105 ) (244 ) Restructuring, impairment and other (342 ) (433 ) (412 ) Separation and merger related (184 ) (153 ) (373 ) Other non operating income, net (84 ) 202 80 Interest expense, net (237 ) (223 ) (131 ) Total $ 753 $ 680 $ (335 ) (1) Inventory impairments and related charges are reported in the "Cost of goods sold" caption of the consolidated and combined statements of income (loss). 2017 includes $87 million of adjustments to write-up the acquired inventory to its estimated fair value on acquisition of BHI as this inventory was used or sold in the six months ended December 31, 2017. The following table presents total assets by segment at December 31: Segment assets 2019 2018 Oilfield Services $ 30,317 $ 30,647 Oilfield Equipment 7,645 7,298 Turbomachinery &amp; Process Solutions 8,365 8,529 Digital Solutions 3,983 4,063 Total segment 50,310 50,537 Corporate and eliminations (1) 2,903 1,697 Total $ 53,213 $ 52,234 (1) Corporate and eliminations in total segment assets includes adjustments of intercompany investments and receivables that are reflected within the total assets of the four reportable segments. During 2019, we transferred the $2.1 billion Baker Hughes trade name indefinite-lived intangible asset from Oilfield Services to Corporate due to the separation of GE, resulting in the re-branding of Baker Hughes. The following table presents depreciation and amortization by segment for the years ended December 31: Segment depreciation and amortization 2019 2018 2017 Oilfield Services $ 985 $ 1,003 $ 613 Oilfield Equipment 175 173 187 Turbomachinery &amp; Process Solutions 116 156 174 Digital Solutions 103 112 119 Total Segment 1,379 1,444 1,093 Corporate 39 42 10 Total $ 1,418 $ 1,486 $ 1,103 The following table presents net property, plant and equipment by its geographic location at December 31: Property, plant and equipment - net 2019 2018 2017 U.S. $ 2,594 $ 2,654 $ 3,369 Non-U.S. 3,646 3,574 3,590 Total $ 6,240 $ 6,228 $ 6,959