Year	% of revenue
1972	2.946273830155979
1973	3.111111111111111
1974	3.0214424951267054
1975	3.1572164948453607
1976	4.062229904926534
1977	4.4928522804629
1978	4.65230166503428
1979	5.301339285714286
1980	6.441080439299496
1981	6.6440121865479265
1982	6.60253164556962
1983	6.016815554387809
1984	6.849972024618337
1985	7.228126364827486
1986	7.21328159786273
1987	6.126418152350081
1988	5.133433815054526
1989	3.191906517135911
1990	4.027830971530704
1991	3.4633359296761994
1992	3.4872871471891767
1993	2.4160696727068407
1994	3.064043532858937
1995	2.741949140583105
1996	2.3670921165226404
1997	2.488428476967159
1998	3.564415196053271
1999	5.550454655340766
2000	5.115807090556086
2001	5.073676663037671
2002	4.404042058728748
2003	3.922079734061467
2004	4.970066421450516
2005	5.353721897746728
2006	5.895697001516856
2007	5.696353477017722
2008	5.82134744052886
2009	4.692504498691506
2010	5.036718715508326
2011	5.068163438266313
2012	5.235023926923566
2013	5.171815350740829
2014	5.263238351899811
2015	4.992360710066233
2016	4.33274674039728
2017	4.004679444782009
2018	3.646987867955487
2019	3.669571786165711
2020	3.843998517336817
2021	3.325153193255151
2022	3.5979328479696004