Year	% of revenue
1973	7.355202460276784
1974	6.66592353137889
1975	7.780782240488315
1976	6.8536667507511755
1977	7.725269904870396
1978	8.114014539764415
1979	8.903574903064257
1980	8.870489765007271
1981	9.518115968263423
1982	9.565355437066454
1983	9.29404078625627
1984	9.371902769386411
1985	9.2522925498
1986	9.84455667994091
1987	10.126749593628471
1988	9.023807199610525
1989	9.022678596805425
1990	9.281746852768457
1991	8.50845834302772
1992	8.970009409891372
1993	8.816369413694142
1994	7.403946501055451
1995	8.102342131408898
1996	7.638780741177742
1997	7.005740780845603
1998	6.422021492993613
1999	6.181445730779974
2000	6.788913369070543
2001	6.907311171569522
2002	7.272875995201221
2003	7.276461989199386
2004	7.92207474588692
2005	9.046622235113707
2006	9.171631868253254
2007	9.201626482869617
2008	9.673777426644769
2009	10.453814118219467
2010	10.193597098095214
2011	10.322210875979286
2012	12.01678970691388
2013	11.423495268463046
2014	9.865555023027559
2015	9.148862908957156
2016	9.12111821583117
2017	8.37597551772885
2018	8.814837182499954
2019	9.052450274071159
2020	9.108899211009401
2021	9.050702454583314
2022	9.011869076193877