Table:
|  | Year Ended December 31, |  | Change |  |
| --- | --- | --- | --- | --- |
|  | 2019 | 2018 | $ | % |
|  |  | (dollars in thousands) |  |  |
| General and administrative | $ 46,820 | $ 31,462 | $ 15,358 | 48.8% |
| % of revenue | 23% | 21% |  |  |
Paragraphs:
General and Administrative Expense
General and administrative expense increased by $15.4 million in 2019 compared to 2018. The increase was primarily due to a $9.8 million increase in employee-related costs, which includes stock-based compensation, associated with our increased headcount from 89 employees as of December 31, 2018 to 113 employees as of December 31, 2019. There was an additional increase of $3.7 million in depreciation and amortization, $0.8 million to support compliance as a public company, a $0.6 million increase in office related expenses to support the administrative team, and an increase of $0.2 million in software subscription costs.
Question:
What was the increase in the cost of depreciation and amortization from 2018 to 2019?
Answer: $3.7 million