Year	% of revenue
1973	26.66141366043774
1974	27.12459132144263
1975	28.21316614420067
1976	27.23704866562011
1977	27.88236129857214
1978	31.044293566117037
1979	32.53286906405715
1980	33.01204819277108
1981	32.19705322559193
1982	33.595790814629225
1983	31.66743918406319
1984	32.591553747086365
1985	27.798555400119906
1986	29.809501099541635
1987	28.51026032295534
1988	28.995950008696315
1989	29.92560456928305
1990	27.436904496555453
1991	30.408163265306122
1992	34.694009783911575
1993	34.788580762519956
1994	33.592986850344396
1995	32.126357503373875
1996	32.859791586277886
1997	32.45463405704977
1998	31.658725643657426
1999	33.27221907034359
2000	33.15615764665202
2001	31.951118968528114
2002	32.654879931252886
2003	32.766646778443594
2004	31.913725968993276
2005	32.31854722897649
2006	31.9699366132689
2007	31.518972177019467
2008	31.945694505915306
2009	33.63334990644904
2010	33.81414978673201
2011	33.11700955122913
2012	32.709354625218864
2013	32.381106030639
2014	32.55648271515327
2015	32.197771953697604
2016	33.07079332012942
2017	32.30807465177103
2018	32.92839253798349
2019	32.685274542958496
2020	33.512291940967245
2021	32.4061337883941
2022	32.24472632980587