Year	% of revenue
1990	9.870580638217726
1991	11.533032017746777
1992	11.660818713450292
1993	12.830677889673831
1994	12.914324358595039
1995	11.819765960231148
1996	13.476075436408976
1997	16.56769031039658
1998	17.54003561711737
1999	18.739700139738513
2000	17.087084764642366
2001	15.275442679663042
2002	14.387231195148475
2003	12.583706511976242
2004	12.626480808576101
2005	12.541673102835116
2006	14.587647077608166
2007	17.237199074685172
2008	18.433285116412545
2009	19.23436324193802
2010	16.25802581625358
2011	17.05001514983717
2012	17.99702874782944
2013	19.39667196509084
2014	18.68571123729587
2015	19.14786993521502
2016	21.78746494726137
2017	22.149418994025247
2018	22.63567772110831
2019	22.524627068125366
2020	27.2394701051844
2021	24.58668672882459