Year	% of revenue
1991	32.36364453230299
1992	38.00058965161417
1993	30.095106079858304
1994	36.09402957448121
1995	40.994180305481436
1996	38.42765962457901
1997	49.98795122656514
1998	42.82617882549103
1999	49.798736307970046
2010	17.051037872471145
2011	22.772567409144198
2012	29.181049823971595
2013	31.53227729856501
2014	36.72239225129774
2015	39.887386797777815
2016	43.442949482965965
2017	41.43781943420653
2019	45.98694971782019
2020	45.271910731778725
2021	46.41651102357979