Year	% of revenue
1972	40
1973	26.31578947368421
1974	26.923076923076923
1975	30.952380952380953
1976	29.03225806451613
1977	31.11111111111111
1978	31.944444444444443
1979	32.78688524590164
1980	34.00286944045911
1981	36.45569620253165
1982	37.67697954902989
1983	31.561851484255165
1984	28.433539385986116
1985	27.284010138957175
1986	27.442808155636033
1987	30.869179828953296
1988	35.92633451025024
1989	32.726928744971524
1990	30.74833829002324
1991	29.09165656915354
1992	30.327902831322806
1993	34.07497154605867
1994	37.854196463735676
1995	36.38652817123072
1996	32.35709219080213
1997	33.44618549061943
1998	33.21051438667047
1999	33.46755500932544
2000	34.47540404576015
2001	34.1430400568604
2002	30.23093804572993
2003	29.244134643392012
2004	29.563671508633192
2005	30.802926625931953
2006	33.11184887397633
2007	33.58845367268426
2008	30.542525288980276
2009	27.956768117574498
2010	27.40231381117175
2011	28.362413813507224
2012	28.309532573417094
2013	29.446401385304853
2014	28.925917631674775
2015	29.8280575014456
2016	30.326604671130074
2017	34.31842731606655
2018	31.592627617789464
2019	31.647837737079858
2020	32.05731501407058
2021	35.69977405075866
2022	37.38827996700792