19. Segment information The Company defines its operating segments as components of its business where separate financial information is available and used by the chief operating decision maker (CODM) in deciding how to allocate resources to its segments and in assessing performance. The Companys CODM is its Chief Executive Officer. The Company has identified two reportable segments for financial reporting purposes: Software and Client Engineering Services. The primary measure of segment operating performance is Adjusted EBITDA, which is defined as net income (loss) adjusted for income tax expense (benefit), interest expense, interest income and other, depreciation and amortization, stock-based compensation expense, restructuring charges, asset impairment charges and other special items as determined by management. Adjusted EBITDA includes an allocation of corporate headquarters costs. The Software reportable segment derives revenue from the sale and lease of licenses for software products focused on the development and application of simulation technology to synthesize and optimize designs, processes and decisions for improved business performance. The Software segment also derives revenue from software support, upgrades, training and consulting services focused on product design and development expertise and analysis support from the component level up to complete product engineering at any stage of the lifecycle. To a much lesser extent, the Software segment also includes revenue from the sale of hardware products, primarily as a result of recent business acquisitions. The Client Engineering Services reportable segment provides support to its customers with long-term ongoing product design and development expertise in its market segments of Solvers &amp; Optimization, Modeling &amp; Visualization, Industrial and Concept Design, and high performance computing. The Company hires simulation specialists, industrial designers, design engineers, materials experts, development and test specialists, manufacturing engineers and information technology specialists for placement at customer sites for specific customer-directed assignments. The All other represents innovative services and products, including toggled  , the Companys LED lighting business. toggled  is focused on developing and selling next-generation solid state lighting technology along with communication and control protocols based on intellectual property for the direct replacement of fluorescent light tubes with LED lamps. Other businesses combined within Other include the Companys WEYV business, which was terminated in the third quarter of 2019, and potential services and product concepts that are still in their development stages. See Note 4  Acquisitions and disposals for further information about the termination of the WEYV business. Inter-segment sales are not significant for any period presented. The CODM does not review asset information by segment when assessing performance, therefore no asset information is provided for reportable segments. The accounting policies of the segments are the same as those described in Note 2Summary of significant accounting policies. The following tables are in thousands: Year ended December 31, 2019 Software CES All other Total Revenue $ 401,278 $ 48,987 $ 8,650 $ 458,915 Adjusted EBITDA $ 38,834 $ 5,255 $ (4,540 ) $ 39,549 Year ended December 31, 2018 Software CES All other Total Revenue $ 341,306 $ 47,852 $ 7,221 $ 396,379 Adjusted EBITDA $ 48,643 $ 5,155 $ (3,618 ) $ 50,180 Year ended December 31, 2017 Software CES All other Total Revenue $ 280,214 $ 46,510 $ 6,609 $ 333,333 Adjusted EBITDA $ 22,864 $ 4,966 $ (5,313 ) $ 22,517 Year ended December 31, 2019 2018 2017 Reconciliation of Adjusted EBITDA to GAAP income (loss) before income taxes: Adjusted EBITDA $ 39,549 $ 50,180 $ 22,517 Stock-based compensation expense (8,528 ) (3,339 ) (47,281 ) Interest expense (6,371 ) (200 ) (2,160 ) Interest income and other (1) 260 (4,883 ) 2,260 Depreciation and amortization (21,522 ) (14,734 ) (11,747 ) Income (loss) before income taxes $ 3,388 $ 27,024 $ (36,411 ) (1) Includes for the year ended December 31, 2019 a) nonrecurring acquisition related costs of $0.6 million, b) nonrecurring severance expense of $0.4 million, and c) impairment charges for royalty contracts of $1.0 million of expense. Includes for the year ended December 31, 2018 a) nonrecurring costs from the acquisition of Datawatch of $10.4 million, b) gain on the sale of a building of $4.4 million, and c) impairment charges for royalty contracts and trade names of $2.8 million of expense. Includes for each of the years ended December 31, 2018 and 2017, a non-recurring adjustment for a change in estimated legal expenses of $2.0 million of income in each year. Revenue is attributed to geographic areas based on the country of origin. The following table provides sales to external customers and long-lived assets for each of the geographic areas in which the Company operates (in thousands): Revenue Long-lived assets (1) Year ended December 31, December 31, 2019 2018 2017 2019 2018 United States $ 219,053 $ 186,026 $ 142,679 $ 55,319 $ 63,266 Other countries 14,753 8,604 6,404 10,190 11,447 Total Americas 233,806 194,630 149,083 65,509 74,713 Germany 50,102 45,664 43,751 3,405 4,305 France 17,210 16,154 18,128 1,224 1,583 Other countries 49,312 42,846 40,050 11,316 4,729 Total Europe, Middle East and Africa 116,624 104,664 101,929 15,945 10,617 Japan 37,757 35,478 33,686 2,036 2,045 Other countries 70,728 61,607 48,635 8,941 2,957 Total Asia Pacific 108,485 97,085 82,321 10,977 5,002 Total $ 458,915 $ 396,379 $ 333,333 $ 92,431 $ 90,332 (1) Includes property and equipment, net and definite-lived intangible assets, net.