Table:
|  |  |  | Year Ended December 31, |  |  |
| --- | --- | --- | --- | --- | --- |
|  | 2019 | 2018 | 2017 | 2016 | 2015 |
| Stock-based compensation expense data: |  |  |  |  |  |
| Sales and marketing | $2,075 | $1,196 | $561 | $536 | $372 |
| General and administrative | 6,474 | 4,901 | 2,638 | 1,430 | 2,486 |
| Research and development | 12,054 | 7,332 | 4,214 | 2,035 | 1,266 |
| Total stock-based compensation expense | $20,603 | $13,429 | $7,413 | $4,001 | $4,124 |
Paragraphs:
ITEM 6. SELECTED FINANCIAL DATA
The selected consolidated statements of operations data for the years ended December 31, 2019, 2018 and 2017 and the selected consolidated balance sheet data as of December 31, 2019 and 2018 are derived from our audited consolidated financial statements included elsewhere in this Annual Report. The selected consolidated statements of operations data for the years ended December 31, 2016 and 2015 and the selected consolidated balance sheet data as of December 31, 2017, 2016 and 2015 are derived from our audited consolidated financial statements not included in this Annual Report. Our historical results are not necessarily indicative of the results to be expected in the future. The selected financial data should be read together with Item 7. "Management’s Discussion and Analysis of Financial Condition and Results of Operations" and in conjunction with our consolidated financial statements, related notes, and other financial information included elsewhere in this Annual Report. The following tables set forth our selected consolidated financial and other data for the years ended and as of December 31, 2019, 2018, 2017, 2016 and 2015 (in thousands, except share and per share data).
Information about prior period acquisitions that may affect the comparability of the selected financial information presented below is included in Item 1. Business. Information about the $28.0 million expense recorded in general and administrative expense in 2018, which relates to the agreement reached to settle the legal matter alleging violations of the Telephone Consumer Protection Act, or TCPA, and may affect the comparability of the selected financial information presented below, is disclosed in Item 3. “Legal Proceedings.” Information about the $1.7 million of interest recorded within interest income and the $6.9 million of gain recorded within other income, net, in 2019, which relates to promissory note proceeds received from one of our hardware suppliers and proceeds from an acquired promissory note, and may affect the comparability of the selected financial information presented below, is disclosed in Item 7. "Management’s Discussion and Analysis of Financial Condition and Results of Operations."
Certain previously reported amounts in the consolidated statements of operations for the years ended December 31, 2018, 2017, 2016 and 2015 have been reclassified to conform to our current presentation to reflect interest income as a separate line item, which was previously included in other income, net.
Question:
What was the percentage change in the Total stock-based compensation expense between 2018 and 2019?
Answer: (20603-13429)/13429 = 53.42