Year	% of revenue
1990	4.948214790771592
1991	4.7750739902698935
1992	5.054661053900001
1993	7.07744568982924
1994	8.418419726354694
1995	9.853666386950675
1996	9.775476745189405
1997	8.231290911114334
1998	7.667537422769753
1999	8.603844313287606
2000	11.465342275364558
2001	14.093441244481816
2002	15.35870048419459
2003	18.154830328584215
2004	37.39541094594221
2005	27.869524075396722
2006	27.423348762125404
2007	15.204655971206494
2008	13.601652229153762
2009	13.545942934233096
2010	13.348879219895817
2011	12.373075807901813
2012	7.081766284661796
2013	8.89164852260031
2014	9.093141446241484
2015	8.553033848704379
2016	8.264307401477392
2017	9.439437741374892