Year	% of revenue
1972	30.801687763713083
1973	36.25632377740304
1974	41.06145251396648
1975	39.981617647058826
1976	41.266527487821854
1977	46.923488496522204
1978	47.83802333562114
1979	46.949869136299576
1980	49.05321062096689
1981	51.673016972635956
1983	48.1725844257314
1984	49.44872598547144
1985	37.989835079348616
1986	43.51215757817622
1987	42.59499947048686
1988	39.54671468175712
1989	43.16743908770985
1990	42.02841428886535
1991	41.01870363416788
1992	39.564047453840814
1993	35.39536401852592
1994	33.05463841378488
1995	31.143319599764567
1996	31.942696305914815
1997	35.89576176599185
1998	40.17723874196575
2008	17.68034047348824
2009	17.70518966522758
2010	17.32182800495276
2011	17.571122951572644
2012	17.673498178889844
2013	16.349422029490988
2014	17.569644303658695
2015	16.97998236216554
2016	17.55846325735641
2017	18.09848925985419
2018	19.34534001625683
2019	19.45537239509446
2020	18.599851421902734
2021	20.893149997955877
2022	20.872991845406432