Year	% of revenue
1972	27.55632582322357
1973	25.77777777777778
1974	26.900584795321635
1975	21.789900603244583
1976	25.581020925615817
1977	25.518359110993988
1978	26.315792935633116
1979	25.595279532327005
1980	27.62357596539053
1981	27.99220272904487
1982	25.520750225256876
1983	23.360378634212307
1984	23.350561840846396
1985	25.06710537708892
1986	25.24648559251956
1987	27.94152386836514
1988	30.146190865340962
1989	29.46832870227442
1990	30.5801885002746
1991	30.335161640927183
1992	30.327902831322806
1993	27.12502400614557
1994	24.462504772485644
1995	25.52169527419874
1996	24.767252844687455
1997	23.319664268640096
1998	24.214762628541926
1999	23.791075407629144
2000	25.008529512111906
2001	25.0268536748475
2002	23.282975203490416
2003	23.626208187891827
2004	24.11864126025105
2005	25.90496902661399
2006	25.5292159236576
2007	26.774048257372655
2008	24.926939237370178
2009	22.958971017005062
2010	22.263745500272215
2011	23.69310116066184
2012	21.25211679037962
2013	22.650851431391906
2014	24.26930759599394
2015	24.964923860137723
2016	23.677525370224256
2017	24.591797187528964
2018	24.509584697662792
2019	25.730191177954904
2020	23.605064267398536
2021	27.512464440252078
2022	28.88317189777841