Year	% of revenue
1973	7.289918546109473
1974	8.308539596125852
1975	11.45090136702795
1976	12.89492111875441
1977	13.25676115998695
1978	11.878478360505474
1979	12.08888794917065
1980	13.546686503444496
1985	20.443095926318154
1986	21.908721138791538
1987	20.11213981228565
1988	21.755397985102345
1989	23.072351444102537
1995	26.793858580231873
1996	26.332928901886802
1997	21.130105900151285
1998	19.91365915751994
1999	16.013899510180917
2000	16.12155806359408
2001	15.923232657108624
2002	14.461542185297018
2003	13.213631783447234
2004	12.34212419404389
2005	12.171801998271805
2006	11.48163804215657
2007	11.774477264642627
2008	12.09889767304295
2009	10.631646487663444
2010	10.537509020612399
2011	11.510483593188455
2012	12.381451007426538
2013	11.50596284477003
2014	11.024375919564665
2015	9.931352167865635
2016	9.448886558599497
2017	9.168792193744782
2018	8.959191567819701
2019	8.140468355713617
2020	8.276070443255104
2021	8.342015762083358
2022	10.06513565731987