Year	% of revenue
1985	9.105431309904153
1986	6.405097250167673
1987	16.44003263530052
1988	17.066831683168317
1989	14.898351370486498
1993	15.932563791008505
1994	18.459559414696898
1995	22.76331747364493
1996	22.32072325111911
1997	22.286028949024544
1998	21.25045972784112
1999	20.079338842975204
2000	18.631690889755408
2005	12.333842083986228
2006	17.388197616287588
2007	19.155358998158643
2008	14.080200210237425
2009	18.009057570922998
2010	15.83595298559391
2011	7.705401942683826
2012	10.320106780993783
2013	7.807042589852535
2014	8.026662608583454
2015	9.662524506030227
2016	8.62780298286706
2017	8.263675754441142
2018	6.65779443091547
2019	5.284385474592504
2020	9.376580876250745