Year	% of revenue
1972	23.672230652503792
1973	21.338112305854242
1974	17.83339851388346
1975	19.772879091516366
1976	22.13225371120108
1977	22.21344913804448
1978	25.692273336310855
1979	26.53288740245262
1980	25.065981386303655
1981	27.310714731196207
1982	29.037970727642065
1983	30.256504550887193
1984	33.708544232076754
1985	32.815188192327426
1986	31.825884346536746
1987	33.929068795840685
1988	34.69853159299911
1989	33.90684069648721
1990	34.881995339694605
1991	34.0758922339584
1992	33.3018092568199
1993	37.27838551490004
1994	38.426803243704654
1995	36.770778805327744
1996	35.09494953104829
1997	35.57075737434679
1998	35.07296976468124
1999	34.60368583538651
2000	34.533396183878835
2001	33.10369123576154
2002	33.71105089994194
2003	35.28972259990955
2004	36.18983384022887
2005	35.19110029491047
2006	34.42615557247336
2007	33.6809862858088
2008	31.348823735730686
2009	32.083664755557606
2010	34.75043203057773
2011	33.40211975572065
2012	34.16862241797313
2013	33.554980940658396
2014	32.77359235963332
2015	33.292890616631055
2016	32.81748620742319
2017	32.436016068774414
2018	34.1673701372738
2019	33.78481919244262
2020	33.21746878501482
2021	32.898512163712546
2022	31.838847949008