Year	% of revenue
1972	34.33127726794042
1973	35.00709219858156
1974	33.3291219204043
1975	30.409731113956468
1976	27.9296875
1977	27.896568871208355
1978	29.194956353055286
1979	30.185507594404754
1980	29.643908969210177
1981	30.147884687383
1982	29.08518395757375
1983	29.589624894375255
1984	28.394304349229927
1985	30.051103434493392
1986	30.75272235911295
1987	29.378003507413396
1988	30.07142857142857
1989	29.263937445960682
1990	30.60000999184
1991	32.9641160085204
1992	31.96139793226615
1993	34.49901622303894
1994	37.36293859649123
1995	34.98320727026417
1996	33.42142330136159
1997	33.36525567342156
1998	33.01624104661027
1999	33.02921061782775
2000	32.12184233723024
2001	34.753253685700976
2002	37.340057420469186
2003	37.36503518799589
2004	36.76491327034269
2005	35.87262597191102
2006	36.06776303525871
2007	35.470915441335
2008	37.0717312062313
2009	38.811774299543714
2010	38.9624579089369
2011	38.49861424153475
2012	38.73424317781545
2013	38.34152162495965
2014	38.3556225204496
2015	37.780542548385476
2016	37.856139014571426
2017	37.57162397429579
2018	37.7285435335292
2019	37.342638867221005
2020	38.18959555966245
2021	37.28202773952117
2022	37.39659001872065