Year	% of revenue
1972	10.042036431574031
1973	8.973128598848362
1974	9.748121347063734
1975	9.750399766036633
1976	9.293696731441537
1977	9.557688675621229
1978	9.996699590267536
1979	10.05371675512826
1980	10.163051094049859
1981	10.466245578216824
1982	10.834199644413745
1983	10.597302504816955
1984	11.304447645257817
1985	11.628552799980673
1986	11.651285431773237
1987	11.27647930376283
1988	10.300189160292787
1989	12.183358167986825
1990	11.011165104844888
1991	10.666551694403726
1992	11.246780925317468
1993	10.800730666096781
1994	9.456398509642572
1995	10.829413435065497
1996	9.586619256669513
1997	9.9012631614155
1998	9.38490256581919
1999	9.239661604750145
2000	8.958165454704323
2001	8.332945684051055
2002	8.42215909697504
2003	8.724609347595283
2004	8.274671473988228
2005	8.893568856526468
2006	9.229899586953426
2007	9.296801228170368
2008	10.00262263149338
2009	10.474837029167983
2010	12.298887560908339
2011	10.558004739158907
2012	10.476660718575117
2013	10.876090597584607
2014	10.361775607531104
2015	10.828915124987947
2016	9.593462724158506
2017	9.209954126866258
2018	10.196693713013005
2019	10.558612384391196
2020	10.399366858995414
2021	9.727680847758343
2022	10.21280187957213