Year	% of revenue
1973	20.158385671677166
1974	21.297844529696924
1975	20.516813470241882
1976	20.09751536200907
1977	22.2517343992351
1978	21.146232438242723
1979	21.682985289981524
1980	21.99801555681354
1981	21.632480439839348
1982	20.27315944361997
1983	21.74253915770454
1984	21.365261616851683
1985	23.204820992059943
1986	20.893495208362847
1987	21.83595217680323
1988	22.872455939172962
1989	21.19980377041134
1990	20.904295461807642
1991	25.98357111975786
1992	19.951961569255424
1993	18.80863977800354
1994	19.16427393243326
1995	22.02433610088555
1996	19.422630147456307
1997	22.721896265238165
1998	22.50099211517715
1999	20.69303811792075
2000	22.01278938473297
2001	21.2440359281673
2002	21.499217942916257
2003	19.84857063890926
2004	19.483182756717795
2005	20.16881958528154
2006	19.717621208474785
2007	20.658124709638713
2008	21.01082792460368
2009	18.864673922187862
2010	17.541927116689713
2011	16.29918735122886
2012	16.09640737277509
2013	16.454260078601973
2014	18.147818570360684
2015	17.78845567520763
2016	18.51536038276605
2017	19.43659760279033
2018	19.27208894090111
2019	19.016847071400136
2020	17.95994849200529
2021	20.16402666680806
2022	19.988218744986057