Year	% of revenue
1973	8.846808016103541
1974	9.007588257637
1975	9.407216494845361
1976	9.27232496973239
1977	9.551047875408559
1978	9.804467330039648
1979	10.026041666666668
1980	10.121371403298376
1981	10.090620653517833
1982	10.68729893671878
1983	10.59708861898691
1984	11.304447645257817
1985	11.628552799980673
1986	11.460426926264246
1987	10.92842898293817
1988	10.20552090100389
1989	10.155755044900893
1990	10.414264539360822
1991	10.245354400801157
1992	9.824975064862919
1993	10.227552412355454
1994	9.120899260797842
1995	8.150293592611547
1996	7.5188353300663024
1997	6.919079457216283
1998	7.060374639526564
1999	6.757219236149078
2000	7.004866270628477
2001	8.248972437953356
2002	7.380904894266933
2003	7.994325333459888
2004	8.22897384721978
2005	8.71934038455115
2006	9.131193550915814
2007	9.166626749505145
2008	9.304536149481748
2009	10.447224404937874
2010	10.193597098095214
2011	10.322210875979286
2012	9.832906907291632
2013	10.066448495490253
2014	9.815420018367075
2015	9.509816105097514
2016	8.881803442638791
2017	8.684553502248544
2018	8.985681195479106
2019	8.650122730488068
2020	9.146659588398293
2021	9.103803306715108
2022	9.288389877037117