Year	% of revenue
1973	1.8746674307232616
1974	1.5889092865734022
1975	0.22602254779151287
1976	0.21213494253820467
1977	0.1873574454219616
1978	1.7625875728409635
1979	1.721093972999544
1980	1.634108476988257
1981	1.3696555901219618
1982	1.5276322506112243
1983	1.6160276661856254
1984	1.76470588235294
1985	1.7558663530763587
1986	1.726881205877941
1987	1.6511162807329707
1988	1.1931927528707156
1989	1.1879617519217407
1995	5.184744928156132
1996	4.433550510682367
1997	5.249837907931705
1998	5.135830543639272
1999	4.267773543703517
2000	4.11603190964132
2001	3.9567408998884437
2002	4.803570960330955
2003	7.126025775237109
2004	5.600810583379606
2005	4.431958882434136
2006	4.694210908104102
2007	4.537770423964728
2008	4.376853532002654
2009	6.269990721249946
2010	4.83377381003586
2011	5.340018842314365
2012	5.406463558995444
2013	5.22690660966183
2014	4.887572226929442
2015	4.63350432974889
2016	5.510843127830937
2017	4.909035091997785
2018	4.777548444660288
2019	4.5234109359716586
2020	4.590075931692278
2021	4.6613720399758
2022	4.704064499408584