Year	% of revenue
1990	18.667533915629065
1991	18.32180099405516
1992	17.279380111924237
1993	16.30901287553648
1994	16.874717029946318
2000	22.535211267605636
2001	19.924033149171272
2002	28.123799646615964
2003	23.860340596415558
2004	23.395449955035055
2005	25.9504652732107
2006	24.704471431677455
2007	22.342789185987304
2008	23.921464181416237
2009	24.74588717440581
2010	16.74246095942084
2011	12.090484737755375
2012	9.803115095536729
2013	8.550728812435361
2014	9.855907179599544
2015	13.483396478716292
2016	14.788320826612434
2017	16.05245525031109
2020	15.493355951371218