Year	% of revenue
1972	3.1645569620253164
1973	3.372681281618887
1974	3.212290502793296
1975	3.0330882352941178
1976	2.8531663187195546
1977	2.7287319422150884
1978	2.4708304735758406
1979	2.999798671230119
1980	2.9620226383158785
1981	5.355039833737444
1983	7.873947391266603
1984	13.824256056639255
1985	12.361788196245204
1986	15.45423448590405
1987	18.41261589117061
1988	19.254051273257307
1989	19.80314481131773
1990	22.575402005416723
1991	18.873722561068433
1992	15.234646042410601
1993	19.422668925192884
1994	23.789339349604614
1995	15.091115847700246
1996	18.292841280498152
1997	36.120223783750724
1998	49.85798379529196
2008	14.581605757052376
2009	14.103775309213166
2010	10.854660335168278
2011	9.373232710277664
2012	8.762194958960158
2013	7.110740984410261
2014	7.1441449558441406
2015	6.281135822299595
2016	6.153379902623289
2017	6.89391661988913
2018	9.119468161650582
2019	8.298468896399513
2020	10.293712832576137
2021	10.519684157514233
2022	18.169382095840454