Year	% of revenue
1972	12.53438978760867
1973	12.50644928283975
1974	11.042193748469762
1975	9.956765005086469
1976	10.08608778828781
1977	10.582537455302585
1978	11.460785528435139
1979	11.004548900682336
1980	10.085078534031414
1981	9.217101610216547
1982	9.310048258397439
1983	10.3352807813045
1984	10.857437811439121
1985	10.362974870970472
1986	11.340144049663985
1987	11.27647930376283
1988	9.727883794475908
1989	8.410670942658511
1990	7.602451555483636
1991	7.1975650028845966
1992	8.473200628492346
1993	8.58086821324823
1994	9.235874629802915
1995	7.440866992314023
1996	6.966072970293864
1997	6.832418133586963
1998	6.328677236756879
1999	10.760956557928097
2000	11.114282884656838
2001	8.230044620723847
2002	9.457804073458476
2003	8.724609347595283
2004	8.765897438129478
2005	8.475693556635132
2006	9.149022952278543
2007	9.03645227083992
2008	9.097246760192144
2009	10.235703944987334
2010	12.298887560908339
2011	10.716619540340238
2012	10.132201100067547
2013	10.43190586061232
2014	10.256837336353643
2015	10.864956407200653
2016	10.542519614468805
2017	11.399715018523796
2018	10.864688147650838
2019	11.368329360341898
2020	12.120105689237521
2021	11.862077558469352
2022	11.46244042373917