Year	% of revenue
1999	1.5125870196946647
2000	1.1103027349930679
2001	2.562378499190653
2002	2.964578757409812
2003	3.1571797948655336
2004	3.0168082126853757
2005	3.2958946539018625
2006	1.729537051813151
2007	1.9261788535996236
2008	2.737063773001806
2009	7.145223006607575
2010	3.490075809880712
2011	2.4726671490045082
2012	2.7369771629250272
2013	3.051531692600273
2014	3.898477957686049
2015	6.625898705665261
2016	7.998362120042998
2017	5.890195998460305
2018	3.534433021717219
2019	3.230535086222998