Year	% of revenue
1972	17.31266149870801
1973	17.162872154115586
1974	12.229176697159366
1975	8.979450872042825
1976	9.37704918032787
1977	7.980517047583365
1978	9.810089712221833
1979	12.321986139669484
1980	10.7195265114459
1981	10.579318466625399
1982	11.060832721630135
1983	10.462949200214954
1984	9.201939923317168
1985	7.401003493335126
1986	9.924407861582395
1987	8.470920976435071
1988	11.557547381013533
1989	16.18641184954712
1990	19.529029184415712
1991	20.26102306081103
1992	20.216708478236768
1993	20.17607352117566
1994	21.340585617573627
1995	22.165080864439265
1996	23.359539451531795
1997	21.26796697907939
1998	22.32782077437101
1999	24.204822339694605
2000	25.304874837160142
2001	26.525987761261344
2002	26.237378798404887
2003	27.330529773607253
2004	27.16462412140569
2005	25.728475624725256
2006	26.609791261351635
2007	27.008148226647243
2008	24.57145897830201
2009	23.50115057205645
2010	24.653860985123508
2011	23.79471534911345
2012	23.337655649730962
2013	25.234032929517415
2014	27.64111580086393
2015	27.97337190943436
2016	19.900116545060808
2017	30.582350495938606
2018	29.736095142818584
2019	31.143948498198508
2020	33.10884047431134
2021	31.051635791416395
2022	32.860407199606676