Year	% of revenue
1972	44.87577639751553
1973	48.13725490196079
1974	65.46644844517185
1975	65.52173913043478
1976	66.50943396226415
1977	67.3913043478261
1978	66.69712197350388
1979	71.46099290780143
1980	78.01268498942918
1981	72.46966504395844
1982	76.88646117830667
1983	73.5735929340468
1984	67.03161717581713
1985	66.13751412984715
1986	40.36766085162258
1987	47.568701828013396
1988	55.94902025905015
1989	57.539614340219295
1990	61.837941667087904
1991	58.04314511375692
1992	53.87126073649916
1993	49.328811392450014
1994	47.35750996962324
1995	46.10754613739243
1996	50.24753845983453
1997	57.0465271318238
1998	61.832671246629204
1999	59.495255305211735
2001	30.680062772566757
2002	32.055105423926726
2003	32.92687344925539
2004	28.18629699116516
2008	33.30096859873604
2009	37.421964664044474
2010	35.883731588087734
2011	35.61608300907912
2012	34.75911448601624
2013	35.201362341002294
2014	35.25151016035784
2015	39.98837261353781
2016	42.82335386060913
2017	38.81973265355849
2018	38.59531784236912
2019	39.39581791392445
2020	36.09699444791609
2021	34.64640844224638
2022	33.46201375812151