Year	% of revenue
1983	4.653422225200174
1984	4.582561985979181
1985	4.443380161770967
1986	4.473436819296999
1987	4.151902491512532
1988	3.828653535293061
1989	4.182850313713773
1990	4.518286450695463
1991	15.830193838273242
1992	19.70488234385831
1993	21.058044305600156
1994	19.024256348893736
1995	18.34729506616037
1996	19.061101190271362
1997	17.945693954979983
1998	17.916206221358436
1999	18.34978985720925
2000	18.405674277478987
2001	18.714497055744705
2002	18.889631269098732
2003	18.960859023207487
2004	20.633169241215416
2005	20.653427051954328
2006	19.175149115502915
2007	17.106242840778926
2008	18.270193191010932
2009	21.910633585730103
2010	22.06977934485896
2011	22.15995924605196
2012	21.795722820283416
2013	20.8391972098146
2014	20.929255465569447