Year	% of revenue
1990	11.747343565525384
1991	8.663366336633663
1992	9.62651236191478
1993	9.321120689655173
1994	9.297520661157025
1995	9.936055090998524
1996	10.199456029011786
1997	9.79299363057325
1998	8.51063829787234
1999	9.619450317124736
2000	19.04515173945226
2001	19.080118592182696
2002	17.851255541507292
2003	18.55151321721724
2004	20.36058846640765
2005	20.95250080080538
2006	24.664388633884936
2007	39.97512607049412
2008	45.9731017145805
2009	43.572859973694825
2010	45.77976677129102
2011	42.85833996561333
2012	44.94069385872576
2013	45.70176037263556
2014	35.640204642745275
2015	40.44401367883986
2016	42.7413876758855
2017	43.45727886927645