Table:
|  |  | Year Ended December 31, |  |  |  |
| --- | --- | --- | --- | --- | --- |
|  | 2019 | 2018 | 2017 | 2018 to 2019 % change | 2017 to 2018 % change |
|  |  |  | (In thousands, except percentages) |  |  |
| Research and Development | $ 207,548 | $ 160,260 | $ 115,291 | 30% | 39% |
Paragraphs:
Operating Expenses
Research and Development Expenses
Research and development expenses increased $47 million, or 30%, in 2019 compared to 2018. The overall increase was primarily due to increased employee compensation-related costs of $34 million, driven by headcount growth, and increased allocated shared costs of $8 million.
Research and development expenses increased $45 million, or 39%, in 2018 compared to 2017. The overall increase was primarily due to increased employee compensation-related costs of $36 million, driven by headcount growth, and increased allocated shared costs of $6 million.
Question:
What is the driver for an increase in employee compensation-related costs in 2019?
Answer: driven by headcount growth