Year	% of revenue
1972	17.51054852320675
1973	12.141652613827993
1974	8.798882681564246
1975	12.775735294117647
1976	6.819763395963814
1977	5.831995719636169
1978	10.363761153054222
1979	18.38131669015502
1980	20.66010790225325
1981	16.425355039833736
1983	15.869433110513064
1984	12.389837383384343
1985	17.400684576288768
1986	14.616886633790372
1987	12.655363968075173
1988	18.542970647917915
1989	18.03971718492593
1990	17.86108168113657
1991	20.096816424287322
1992	20.00936440510642
1993	25.593566576813338
1994	21.16941943250261
1995	22.502885763755952
1996	17.17303251414701
1997	12.944251045014587
1998	14.814315840455267
2008	17.58449177497951
2009	18.154464863579815
2010	16.7685184813537
2011	17.321852076652306
2012	18.720684467529647
2013	17.731285810070265
2014	17.05293867892268
2015	15.459157403729968
2016	16.029346026620903
2017	15.802730888416894
2018	18.608228025256963
2019	18.638965118447697
2020	17.40422771501375
2021	18.337529873629766
2022	17.50771532213073