Year	% of revenue
1972	35.76227390180878
1973	33.41506129597198
1974	41.83919114106885
1975	48.50630288378518
1976	50.20327868852459
1977	49.512926189584114
1978	46.36490737504369
1979	44.962302947224124
1980	48.58882801800039
1981	49.3032174293781
1982	48.87338208375533
1983	48.000823224065584
1984	49.086746396499336
1985	51.35778988117538
1986	50.78663818962828
1987	52.17976948812858
1988	52.94408497885554
1989	48.6394575845855
1990	46.99797593308925
1991	45.927432981608646
1992	45.23294724351579
1993	48.29265017505821
1994	50.555087198183166
1995	49.974793480505845
1996	49.51122733579725
1997	51.17300909958886
1998	51.42958097118772
1999	50.37753996818275
2000	48.527594113536686
2001	44.4061986074445
2002	45.538492808858344
2003	46.725046250522496
2004	47.99963005345657
2005	42.30914672628997
2006	40.18282715282422
2007	38.71190611803229
2008	30.082324256203613
2009	31.19054189136776
2010	34.39385571018118
2011	33.4263177200816
2012	33.6498239653258
2013	33.38286183054822
2014	31.92184717354658
2015	34.45711378351249
2016	23.748981391599933
2017	35.97209556030349
2018	35.70246607668199
2019	36.40947393580075
2020	37.68277787021279
2021	38.81238671407565
2022	35.330882600481765