Table:
|  | Years ended December 31, |  |  | 2019 vs 2018 | 2018 vs 2017 |
| --- | --- | --- | --- | --- | --- |
|  | 2019 | 2018 | 2017 | % Change | % Change |
|  | (in thousands, except percentages) |  |  |  |  |
| Research and development | $ 355,015 | $ 230,674 | $ 135,997 | 53.9 % | 69.6 % |
| Percentage of total revenues | 22.5 % | 21.5 % | 20.2 % |  |  |
Paragraphs:
Research and Development
Research and development expenses increased $124.3 million, or 53.9%, for the year ended December 31, 2019 compared to the same period in 2018, due to an increase of $114.4 million in employee-related costs ($45.1 million of which related to stock-based compensation and related payroll taxes), a $7.4 million increase in computer hardware and software costs, and a $2.5 million increase in professional services fees, all as a result of growth in our research and development employee base and expanded development programs.
Research and development expenses increased $94.7 million, or 69.6%, for the year ended December 31, 2018 compared to the same period in 2017, due to an increase of $89.6 million in employee-related costs, an increase of $3.1 million in computer hardware and software costs, and a $2.0 million increase in professional services fees, all as a result of growth in our research and development employee base and expanded development programs.
Question:
What is the average research and development expenses for 2017 and 2018?
Answer: (230674+135997)/2 = 183335.5