pre_text: Stock-Based Compensation The Company recognizes stock-based compensation expense in the consolidated statements of operations, based on the department to which the related employee reports, as follows: The Company recognizes stock-based compensation expense in the consolidated statements of operations, based on the department to which the related employee reports, as follows: The total unrecognized compensation cost related to performance-based restricted stock units as of December 31, 2019 was $3.6 million, and the weighted average period over which these equity awards are expected to vest is 1.6 years. The total unrecognized compensation cost related to unvested stock options as of December 31, 2019 was $2.0 million, and the weighted average period over which these equity awards are expected to vest is 2.30 years.
table: Years Ended December 31,
table: 2019 2018 2017
table: (in thousands)
table: Cost of net revenue $577 $489 $332
table: Research and development 16,545 17,953 16,190
table: Selling, general and administrative 14,938 13,279 11,016
table: Restructuring expense — — 5,130
table: $32,060 $31,721 $32,668
question: Analyse this data from a financial earnings document. What was the average Research and development between 2017-2019?