Item 6. Selected Financial Data.
SELECTED CONSOLIDATED FINANCIAL DATA
The following selected historical financial data should be read in conjunction with Item 7, “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” and our consolidated financial statements and the related notes appearing in Item 8, “Financial Statements and Supplementary Data,” of this Annual Report on Form 10-K to fully understand the factors that may affect the comparability of the information presented below.
The selected consolidated financial data in this section are not intended to replace the consolidated financial statements and are qualified in their entirety by the consolidated financial statements and related notes included elsewhere in this Annual Report on Form 10-K.
The following selected consolidated statements of operations data for the years ended December 31, 2019, 2018 and 2017, and the consolidated balance sheet data as of December 31, 2019 and 2018, have been derived from our audited consolidated financial statements included elsewhere in this Annual Report on Form 10-K. The consolidated statements of operations data for the years ended December 31, 2016 and 2015 and the consolidated balance sheet data as of December 31, 2017, 2016 and 2015 have been derived from our audited consolidated financial statements not included in this Annual Report on Form 10-K. The selected consolidated financial data for the year ended December 31, 2019 and as of December 31, 2019 reflects the adoption of ASU No. 2016-02, Leases (Topic 842). The selected consolidated financial data for the years ended December 31, 2019 and 2018 and as of December 31, 2019 and 2018 reflects the adoption of ASU No. 2014-09, Revenue from Contracts with Customers. See Notes 15 and 18 of the notes to consolidated financial statements for a summary of adjustments. The summary consolidated financial data for the years ended December 31, 2018, 2017, 2016 and 2015 and as of December 31, 2018, 2017, 2016 and 2015 does not reflect the adoption of ASU 2016-02. The summary consolidated financial data for the years ended December 31, 2017, 2016 and 2015 and as of December 31, 2017, 2016 and 2015 does not reflect the adoption of ASU 2014-09.
Table:
 |  |  | Year Ended December 31, |  | 
 | 2019 | 2018 | 2017 | 2016 | 2015
 |  |  | (in thousands, except shares and per share data) |  | 
Revenue | $200,882 | $147,094 | $104,352 | $76,846 | $58,720
Cost of revenue(1) | 63,535 | 46,810 | 31,503 | 23,767 | 19,789
Gross profit | 137,347 | 100,284 | 72,849 | 53,079 | 38,931
Operating expenses: |  |  |  |  | 
Sales and marketing(1) | 87,731 | 69,608 | 46,998 | 34,847 | 25,925
Research and development(1) | 50,024 | 41,305 | 22,241 | 14,765 | 11,521
General and administrative(1) | 46,820 | 31,462 | 22,895 | 14,293 | 12,272
Total operating expenses | 184,575 | 142,375 | 92,134 | 63,905 | 49,718
Operating loss | (47,228) | (42,091) | (19,285) | (10,826) | (10,787)
Other expenses, net | (4,597) | (4,628) | (302) | (484) | (599)
Loss before income taxes | (51,825) | (46,719) | (19,587) | (11,310) | (11,386)
(Provision for) benefit from income taxes | (425) | (796) | (47) | 24 | 562
Net loss | $(52,250) | $(47,515) | $(19,634) | $(11,286) | $(10,824)
Net loss per share attributable to common shareholders - basic and diluted | $(1.58) | $(1.63) | $(0.70) | $(0.68) | $(0.88)
Weighted average shares outstanding - basic and diluted | 33,161,656 | 29,107,267 | 27,862,375 | 16,659,561 | 12,257,413


Question: In which year was revenue less than 100,000 thousands?
Answer: 2016, 2015
Calculation: locate and analyze revenue in row 4