Year	% of revenue
1990	3.892411983380713
1991	1.8006430868167203
1992	2.689328743545611
1993	3.0796048808832075
1994	3.6815068493150687
1995	4.100820164032807
1996	3.493679775280899
1997	3.323029366306028
1998	5.003113971351464
1999	4.957599478147423
2000	4.714442340277086
2001	5.548983761694807
2002	3.689998972145133
2003	4.532941824187924
2004	3.5744879682267734
2005	3.7172430297953816
2006	4.0048055492133905
2007	3.2356277033319105
2008	2.0021287322839054
2009	2.930362182226958
2010	4.162491611586582
2011	4.061804322951733
2012	4.959671023890923
2013	6.536189019207887
2014	7.3588197404749645
2015	13.194917121660996
2016	19.072752228483488
2017	21.77174426157959
2018	22.288878836367616
2019	22.196571270467242
2020	31.942212146903653