Year	% of revenue
1973	38.848184683394216
1974	38.345888459834235
1975	41.43020532650733
1976	38.073073279235544
1977	35.9710003258391
1978	34.801283310417126
1979	35.44523263312578
1980	33.92655001778849
1981	34.53941029100018
1982	34.03455038822172
1983	32.4158941889743
1984	32.591553747086365
1985	32.78048079857797
1986	37.49461658075845
1987	39.18780237479639
1988	29.410676750849507
1989	29.105615256912447
1995	34.01032522468306
1996	34.818976016981445
1997	33.80959585044305
1998	31.145216599547908
1999	30.736635044703302
2000	31.37868013269699
2001	31.609098045696815
2002	32.400857643658334
2003	32.865975824442955
2004	33.507356883757225
2005	33.8641983159454
2006	31.90915305893466
2007	32.975487652447484
2008	33.87700940854843
2009	33.93385232153683
2010	33.85075406743993
2011	33.834222235503766
2012	32.95450881527008
2013	32.791664880161214
2014	32.60971304994173
2015	32.58797840360139
2016	31.967783749144346
2017	32.18631380526251
2018	32.92839253798349
2019	33.01505018096932
2020	33.51730793769993
2021	32.4061337883941
2022	31.91671774261896