pre_text: Research and Development Expense Research and development expense increased by $8.7 million in 2019 compared to 2018. The increase was primarily due to a $5.4 million increase in employee-related costs, which includes stock-based compensation, associated with our increased headcount from 229 employees as of December 31, 2018 to 252 employees as of December 31, 2019, a $1.3 million increase in hosting and software related cost to support research and development activities and an increase of $0.4 million in office related expenses to support research and development activities. In addition, a total of $6.5 million of internally-developed software costs during 2019 and $7.7 million of internally-developed software costs during 2018 were capitalized, resulting in an increase of the expense by $1.2 million compared to 2018.
table: Year Ended December 31, Change
table: 2019 2018 $ %
table: (dollars in thousands)
table: Research and development $ 50,024 $ 41,305 $ 8,719 21.1%
table: % of revenue 25% 28%
question: Analyse this data from a financial earnings document. What was the average Research and development expense for 2018 and 2019?