Year	% of revenue
1990	15.542264419256346
1991	13.376135914658239
1992	18.51142344377004
1993	19.556388628553577
1994	21.52867895146639
1995	27.57669512058747
1998	30.15388897264325
1999	28.257210707121942
2012	11.767932052013515
2013	10.8042038496379
2014	11.967647749773468
2015	11.422683198756715
2016	11.757162622751661
2017	12.686448494100436
2018	11.76460286419108
2019	10.970193528882914
2020	11.188125072898442
2021	11.242627064139006