Year	% of revenue
1972	23.877745940783193
1973	27.723428950422896
1974	24.16557591623032
1975	19.859323555821575
1976	18.297331639136015
1977	16.651049475262298
1978	23.245962404024432
1979	27.48572265338995
1980	22.80711858549791
1981	19.8750123019388
1982	19.703398231492127
1983	20.158664172382736
1984	20.176126950911122
1985	20.420150823372435
1986	19.057223264540475
1987	19.06684904144687
1988	18.937583992832636
1989	19.01056493958367
1990	18.26311046020389
1991	18.18821872799812
1992	21.971750443186345
1993	25.774402114160694
1994	28.82104085450063
1995	27.707385987373623
1996	27.77253623809932
1997	27.241983967935873
1998	28.806784219964136
1999	28.44860998555372
2000	30.804431599229293
2001	31.156064668129012
2002	31.97718731109885
2003	35.48550975637917
2004	38.14717365472755
2005	36.81988917401168
2006	36.58810134756232
2007	35.14747995418099
2008	36.456747974168074
2009	34.711040612935086
2010	34.14041173794358
2011	33.425312729948494
2012	34.86247799359289
2013	33.81417120479716
2014	34.26104342030917
2015	34.77021423635107
2016	36.48028150508462
2017	35.39458978702824
2018	35.61560402308904
2019	33.8933503509659
2020	31.65447752939113
2021	31.53553240029697
2022	32.2184583741189