Year	% of revenue
1973	2.699136276391554
1974	2.1398284192880412
1975	2.561662925393658
1976	3.252811915720478
1977	3.0298473798962475
1978	3.9247206367222516
1979	4.167483087002535
1980	4.545759661663731
1981	4.89000278473963
1982	5.952203393719679
1983	6.48884206493632
1984	7.392170164343378
1985	9.916114221045607
1986	10.418073007802514
1987	9.68474986704193
1988	9.642485664842113
1989	9.654637990317202
1990	9.653176582812875
1991	5.593659436199175
1992	6.942689603783969
1993	8.28952140156052
1994	7.156284008838178
1995	8.221385601826647
1996	8.222307961784162
1997	8.110959949326526
1998	7.9423775787387125
1999	7.30488820292033
2000	7.037491256849454
2001	6.604133387133326
2002	6.322142837854081
2003	6.087209767300789
2004	5.842001598162061
2005	5.01210228440838
2006	4.496106021715076
2007	4.398830940670038
2008	4.577512478683341
2009	5.637462581360982
2010	5.5375033898324055
2011	5.688636538018875
2012	6.186433284380177
2013	6.035404530588483
2014	6.107404678729029
2015	5.784112106952028
2016	5.465263009333942
2017	4.762429058791758
2018	4.263551257920132
2019	3.8033979558835487
2020	3.6179939021479073
2021	3.1087890099345623
2022	2.8931955534313074