pre_text: Sales and Marketing Expense Sales and marketing expense increased by $22.6 million in 2018 compared to 2017. The increase was primarily due to a $20.0 million increase in employee- related costs, which includes stock-based compensation, associated with our increased headcount from 215 employees as of December 31, 2017 to 286 employees as of December 31, 2018. The remaining increase was principally the result of a $1.8 million increase in trade show and advertising costs and a $0.8 million increase attributed to office related expenses to support the sales team. The adoption of ASC 606 did not have a material impact on the change in commission expense when compared to year over year.
table: Year Ended December 31, Change
table: 2018 2017 $ %
table: (dollars in thousands)
table: Sales and marketing $ 69,608 $ 46,998 $ 22,610 48.1%
table: % of revenue 47% 45%
question: Analyse this data from a financial earnings document. What is the change in the gross margin between 2017 and 2018?