Year	% of revenue
1990	20.489402033430984
1991	20.831445971110778
1992	22.571421341633137
2014	3.7066307822084137
2015	4.033862043855708
2016	4.321781609673316
2017	4.33709825079294
2018	4.607837134920781
2019	4.797870817883485
2020	4.646211300537182