Year	% of revenue
2010	37.198327989406025
2011	32.93763820080247
2012	29.991414171777592
2013	31.51971439078856
2014	28.79766503870457
2015	25.1687840045085
2016	23.764622474299895
2017	25.43781240451633
2018	26.00474064009947
2019	25.946864926207105
2020	22.690591618285325