Year	% of revenue
1990	20.61127647061464
1991	18.66760174489125
1992	17.941430621288877
1993	13.344841375105412
1994	13.50531051089168
1995	10.701244161407624
1996	13.385451721460004
1997	13.13539745115959
1998	15.266183282729726
1999	27.255714057835608
2000	18.065145933067132
2001	14.307599327307127
2002	11.330153428410087
2003	12.998283531951083
2004	11.540890466156204
2005	13.93947523937626
2006	14.543556398330276
2007	19.09156050519913
2008	21.06206757234483
2009	14.9930212727445
2010	14.859315311455394
2011	18.86182229826777
2012	12.557655301970264
2013	20.06694204014569
2014	14.559003452215627
2015	12.94672942545692
2016	11.771340077850098
2017	12.74939167697883