Year	% of revenue
1972	2.168893864129291
1973	2.057387057387059
1974	1.9998944646720456
1975	2.452674096063068
1976	3.559770621967358
1977	4.01747068544896
1978	4.599841384779832
1979	4.862160120845911
1980	5.089630526255099
1981	5.3966427861737065
1982	6.403903715069048
1983	6.48884206493632
1984	7.392170164343378
1985	8.071494581198012
1986	8.58377726404664
1987	9.576837416481052
1988	9.546376577449875
1989	9.966925436567093
1990	10.282813171422667
1991	10.756433431800472
1992	10.512409927942352
1993	10.703669536695376
1994	10.20832060602358
1995	8.971489542305193
1996	8.756771770765342
1997	8.110959949326526
1998	7.9423775787387125
1999	7.621546340687335
2000	7.891931563748145
2001	7.413882184952196
2002	7.462149281375777
2003	7.070352721543404
2004	6.834130788961704
2005	7.258121017277507
2006	7.024188884520592
2007	6.828980325637614
2008	6.225924850807536
2009	6.826830622021457
2010	6.425470560793918
2011	6.171266389573064
2012	5.999762564366986
2013	5.6319033957203555
2014	5.284840851592739
2015	5.018650162335846
2016	4.606503210148726
2017	4.138206670579482
2018	3.616017986820879
2019	3.1881445893256055
2020	3.1009483098866544
2021	2.495635423389179
2022	2.158090747538539