Year	% of revenue
1975	11.185682326621924
1976	11.757425742574256
1977	10.814904574371402
1978	12.255161461090525
1979	15.95232638093055
1981	9.071329025718992
1982	9.510750329091707
1983	12.721672577935411
1984	12.48431093632332
1985	12.072480181200453
1986	11.180491652425397
1987	11.693791440626883
1988	11.239015365640578
1989	11.76391623411491
1990	13.238609775811462
1991	10.109510407668514
1992	13.49194954363655
1993	13.138660666003805
1994	12.533938665598432
1995	13.34301608615823
1996	16.10049330930789
1997	16.815514161775962
2002	22.138850440737233
2003	21.500830023937706
2004	21.646781700991426
2005	23.88045553644698
2006	19.90929367522611
2007	19.399857819859122
2008	20.206631172287057
2009	21.901640162387377
2010	24.230620645644457
2011	27.611904962939786
2012	27.27960672466427
2013	26.466602417518708
2014	20.552923503582157
2015	26.107816240975225