Year	% of revenue
1990	8.92789517533894
1991	6.107355864811134
1992	5.976367734444368
1993	6.48762157382847
1994	9.098619422324836
1995	10.172687941426616
1996	10.583593203080252
1997	11.207165329780903
1998	12.443574264425953
1999	14.78617157490397
2000	15.145061393024015
2001	16.10049339306981
2002	14.68484374146812
2003	10.580624720269341
2004	11.430963638410446
2005	10.660690160351798
2006	10.89461909402064
2007	13.430063637671388
2008	13.78104232249038
2009	14.486915469602943
2010	15.639942781881972
2011	17.05001514983717
2012	17.99702874782944
2013	19.39667196509084
2014	18.68571123729587
2015	19.14786993521502
2016	21.78746494726137
2017	22.149418994025247
2018	19.2686656509754
2019	21.0622035993908
2020	27.2394701051844
2021	24.58668672882459