Table:
|  |  | Year Ended December 31, |  |
| --- | --- | --- | --- |
| (In thousands) | 2019 | 2018 | 2017 |
| Cost of revenue: |  |  |  |
| Software delivery, support and maintenance | $ 2,075 | $ 2,184 | $ 2,879 |
| Client services | 4,067 | 3,997 | 4,484 |
| Total cost of revenue | 6,142 | 6,181 | 7,363 |
| Selling, general and administrative expenses | 27,348 | 24,213 | 23,497 |
| Research and development | 9,200 | 8,937 | 8,605 |
| Total stock-based compensation expense | $ 42,690 | $ 39,331 | $ 39,465 |
Paragraphs:
11. Stock Award Plan
Total recognized stock-based compensation expense is included in our consolidated statements of operations as shown in the table below. Stock-based compensation expense includes both non-cash expense related to grants of stock-based awards as well as cash expense related to the employee discount applied to purchases of our common stock under our employee stock purchase plan.
The estimated income tax benefit of stock-based compensation expense included in the provision for income taxes for the year ended December 31, 2019 is approximately $5.3 million. No stock-based compensation costs were capitalized during the years ended December 31, 2019, 2018 and 2017. The calculation of stock-based compensation expenses includes an estimate for forfeitures at the time of grant.
This estimate can be revised in subsequent periods if actual forfeitures differ from those estimates, which are based on historical trends. Total unrecognized stock-based compensation expense related to nonvested awards and options was $62.4 million as of December 31, 2019, and this expense is expected to be recognized over a weighted-average period of 2.3 years.
Question:
What is the change in the Total cost of revenue from 2018 to 2019?
Answer: 6142 - 6181 = -39