Year	% of revenue
1972	21.899416749202157
1973	22.12361985347229
1974	21.684485432139066
1975	19.061546286876908
1976	20.66638325007971
1977	19.39980989453673
1978	19.41106017428654
1979	22.251705837755875
1980	23.37369109947644
1981	23.034425319267076
1982	22.036408810741076
1983	23.648412975235438
1984	25.302257251196124
1985	24.536762839495726
1986	23.965584787391133
1987	22.7304884071706
1988	22.76012168873177
1989	21.787789260963635
1990	21.42076944860229
1991	21.231623132472595
1992	20.27928368521274
1993	20.149543799353545
1994	21.387021155497248
1995	21.57676348547718
1996	21.489783519329773
1997	20.51806002422369
1998	20.242755357796614
1999	19.292505682363863
2000	17.905891536996148
2001	24.275761292174412
2002	25.433446682627057
2003	25.820709137594772
2004	25.320995499534284
2005	24.179797366402454
2006	23.627869034817753
2007	23.185464956688822
2008	22.56326021283572
2009	22.659441083708185
2010	24.357425235424685
2011	23.97310547522229
2012	22.180722139285123
2013	23.023208269057676
2014	23.487688566472002
2015	21.32371573731418
2016	21.6581523279389
2017	21.11279566828156
2018	20.469206743700195
2019	19.461760119461953
2020	19.331472386134767
2021	20.036609767002105
2022	17.78524245367363