pre_text: Research and Development Expense Research and development expense increased by $19.1 million in 2018 compared to 2017. The increase was primarily due to a $18.1 million increase in employee-related costs, which includes stock-based compensation, associated with our increased headcount from 159 employees as of December 31, 2017 to 229 employees as of December 31, 2018. The remaining increase was principally the result of a $2.9 million increase in hosting and software related cost to support research and development activities and an increase of $0.3 million in software subscription cost which was offset by a $1.0 million decrease in office related expenses to support research and development activities. A total of $7.8 million of internally-developed software costs during 2018 and $6.3 million of internally-developed software costs during 2017 were capitalized, resulting in a decrease of the expense by $1.4 million compared to 2017.
table: Year Ended December 31, Change
table: 2018 2017 $ %
table: (dollars in thousands)
table: Research and development $ 41,305 $ 22,241 $ 19,064 85.7%
table: % of revenue 28% 21%
question: Analyse this data from a financial earnings document. What is the change in the % of revenue?