Year	% of revenue
1972	10.319053993752789
1973	10.135508849557521
1974	10.360251450676984
1975	10.46774874333295
1976	10.416953350763727
1977	10.052981473357406
1978	10.092325264126401
1979	10.41699106225281
1980	10.204730784801342
1981	9.567967989618255
1982	9.175889919234221
1983	8.688832378734226
1984	8.47312864088301
1990	9.740986868040077
1991	9.907266947726555
1992	10.242424108909198
1993	11.039005186280153
1994	11.337670335710708
1995	11.519602926188762
1996	10.799752619469421
1997	10.660219946110942
1998	10.49207120503017
1999	10.62710359160975
2000	10.30083058147781
2001	10.745640835290256
2002	10.455590772690522
2003	10.767642433658827
2004	11.108631815357684
2005	11.674484334376114
2006	11.605186955119198
2007	11.313485565986504
2008	9.820240489917722
2009	9.299769062615013
2010	9.439983703987547
2011	9.085903341055566
2012	8.963152420229862
2013	9.333039758697428
2014	9.140628201140439
2015	9.140804119421828
2016	8.983529002575212
2017	8.860343241390128
2018	9.110994455755208
2019	8.58751035763084
2020	9.140406280108978
2021	9.182484965856725
2022	9.890331826511584