Year	% of revenue
1973	7.897649529430289
1974	7.605896394000859
1975	8.252988816043194
1976	9.18380977825274
1977	8.769149498151071
1978	9.360652534922348
1979	9.764065335753182
1980	10.010834761796955
1981	10.753212991223986
1982	12.814195382513564
1983	10.753964923196376
1984	11.154974740599561
1985	9.631282245373592
1986	11.460426926264246
1987	10.92842898293817
1988	9.659643435980527
1989	9.785192997985094
1990	11.011165104844888
1991	9.113169381454275
1992	9.407526020816642
1993	9.163101146671247
1994	8.449032087854091
1995	8.563461922668408
1996	8.08328841497472
1997	7.365375757457594
1998	7.222543195832081
1999	6.691101269922658
2000	6.89688981984951
2001	8.144106368988577
2002	7.231045491549007
2004	8.22897384721978
2005	8.893568856526468
2006	9.113364149553083
2007	9.296801228170368
2008	9.446522218742999
2009	10.46824731588639
2010	10.412153452675454
2011	10.364458483376893
2012	10.821120337082686
2013	11.320275334556893
2014	9.374002700380508
2015	9.538143016403886
2016	8.78007788270237
2017	8.243187272350742
2018	8.661382028870234
2019	8.712735103345295
2020	8.685354737233872
2021	9.044275815831318
2022	9.212955373779431