Year	% of revenue
1973	36.50608650608649
1974	37.866458588786
1975	37.14809101426929
1976	36.05322621139847
1977	35.230433801969745
1978	35.780391065339835
1979	36.41596068033366
1980	36.13504899067407
1981	36.83653578390424
1982	38.16267438799687
1983	41.428358283185005
1984	40.02995603227523
1985	39.4783966205978
1986	37.84049298919345
1987	39.49922446266337
1988	40.176830061110316
1989	39.008106819265755
1990	35.46939951434337
1991	36.09141928814068
1992	37.24113221067707
1993	36.79870821451879
1994	40.59189392386043
1995	38.9266707229723
1996	37.254083351644326
1997	37.88669045758811
1998	37.90651771087896
1999	38.564201247710976
2000	38.48284556089494
2001	35.10228447299038
2002	34.906751008834114
2003	36.46165470748686
2004	36.57149357297236
2005	33.897529509592154
2006	34.571731234866824
2007	33.959034852546914
2008	34.92148592942074
2009	34.21793971592207
2010	34.76335852803834
2011	36.57575769806706
2012	38.614082618774965
2013	38.32096804047384
2014	38.14628593112608
2015	37.06276564049766
2016	38.1250853573508
2017	35.76584655239351
2018	36.05929473026589
2019	34.51026853796683
2020	34.894191805493016
2021	33.28105513228217
2022	32.499308273054275