SEGMENT INFORMATION Our operating segments are organized based on the nature of markets and customers. We report our operating results through four operating segments that consists of similar products and services within each segment as described below. OILFIELD SERVICES (OFS) OFS 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 (OFE) OFE 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. OFE 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 (TPS) TPS 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 TPS 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 (DS) DS provides equipment and services for a wide range of industries, including oil &amp; gas, power generation, aerospace, metals, and transportation. The offerings include sensor-based 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 results of operations for the nine months ended September 30, 2018 may not be comparable to the results of operations for the nine months ended September 30, 2017 as it excludes the results of Baker Hughes prior to the date of the business combination. Three Months Ended September 30, Nine Months Ended September 30, Segments revenue 2018 2017 2018 2017 Oilfield Services $ 2,993 $ 2,661 $ 8,554 $ 3,101 Oilfield Equipment 631 613 1,912 2,011 Turbomachinery &amp; Process Solutions 1,389 1,414 4,233 4,644 Digital Solutions 653 614 1,913 1,624 Total $ 5,665 $ 5,301 $ 16,612 $ 11,380 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 (loss), corporate expenses, restructuring, impairment and other charges, inventory impairments, merger and related costs and certain gains and losses not allocated to the operating segments. Three Months Ended September 30, Nine Months Ended September 30, Segment income (loss) before income taxes 2018 2017 2018 2017 Oilfield Services $ 231 $ 88 $ 561 $ (35 ) Oilfield Equipment 6 (41 ) (12 ) 26 Turbomachinery &amp; Process Solutions 132 134 364 508 Digital Solutions 106 77 275 240 Total segment 475 258 1,189 739 Corporate (98 ) (89 ) (294 ) (279 ) Inventory impairment (1) (12 ) (12 ) (88 ) (31 ) Restructuring, impairment and other (66 ) (191 ) (374 ) (292 ) Merger and related costs (17 ) (159 ) (113 ) (310 ) Other non operating income, net 6 4 51 62 Interest expense, net (55 ) (41 ) (164 ) (75 ) Total $ 233 $ (230 ) $ 206 $ (186 ) (1) Charges for inventory impairments are reported in the "Cost of goods sold" caption of the condensed consolidated and combined statements of income (loss).