Year	% of revenue
1990	9.196981328592528
1991	8.86427692429836
1992	8.092134991794895
1993	11.382667463783323
1994	13.330595635861348
1995	15.99707256139383
1996	36.013461040641985
1997	33.06511717314106
1998	30.52457340224568
1999	23.35015837568079
2000	28.08604866641664
2001	28.36530376287576
2002	27.27973952013072
2003	26.79230290192472
2004	29.980671623860015
2005	32.96231976535507
2006	34.964822031863974
2007	32.26880138278844
2008	31.45814007267044
2009	30.700319168944596
2010	32.42503401671509
2011	27.83718393079283
2012	34.39886356885972
2013	32.39524200756637
2014	34.728251132700514
2015	35.66876599478258
2016	46.66140730622871
2017	48.07216711200144