Year	% of revenue
1973	26.14821076359538
1974	25.179386823222437
1975	20.066472787702537
1976	15.288670509307382
1977	17.82304807364473
1978	21.311076898144396
1979	22.595204513399153
1980	20.621172836100843
1981	20.6657018813314
1982	20.84589504959147
1983	20.1346778786559
1984	22.54863281842736
1985	21.932205193699446
1986	21.16800036686309
1987	21.06747305344786
1988	22.430102376818535
1989	25.432249516114364
1990	25.728791716659998
1991	28.244057270324184
1992	29.563631261400307
1993	30.108028164485738
1994	30.418408863735554
1995	30.18078864783736
1996	32.42472309399487
1997	33.3744110975397
1998	35.510879618361486
1999	41.823304133468326
2000	42.664765525982254
2001	42.172547700706666
2002	43.325890242214044
2003	46.17748555632509
2004	46.17667753075237
2005	48.79580833314322
2006	48.715675311489676
2007	52.60256546167709
2008	52.65738548777802
2009	50.66302736862236
2010	55.0626120569337
2011	57.12076227854767
2012	58.48339500139198
2013	58.38818621127182
2014	56.64348980375797
2015	54.00490624262372
2016	56.00906533037288
2017	56.79884136904584
2018	58.087658270571104
2019	58.60120633569282
2020	54.75740528385652
2021	54.12456430131437
2022	51.14243578541745