Year	% of revenue
1972	16.292949576082105
1973	13.767514749262535
1974	11.29110251450677
1975	11.277387667395725
1976	9.749552772808586
1977	9.853879121249957
1978	9.486341571750373
1979	9.348821276198189
1980	9.169510149788907
1981	8.770412025521791
1982	8.141389969089639
1983	8.037645269387077
1984	7.4306863475099645
1990	2.197152705405047
1991	2.137941060291237
1992	2.0565378167118573
1993	1.8866446302468656
1994	1.8641224053927954
1995	1.7348894003954778
1996	1.9101149819974503
1997	1.517800998207654
1998	1.3392245183402283
1999	1.4150091917454792
2000	1.2573941021179758
2001	1.253048534624857
2002	1.2782893682105028
2003	1.27561465052216
2004	1.21741376796363
2005	1.07847144465451
2006	1.0785921971505588
2007	1.0447705911543512
2008	0.9577419751616295
2009	0.9915449630909724
2010	1.0097015384695043
2011	0.9491232240096175
2012	0.9420139052796763
2013	0.9290816409804796
2014	0.9340055744267537
2015	0.8879502183886062
2016	0.9521380614202841
2017	0.881183099312049
2018	0.8738955839330582
2019	0.8840553298053974
2020	0.9447269618902935
2021	0.9232517337670001
2022	0.8918741565113664