Year	% of revenue
1988	30.710636692736504
1989	27.850623434083456
1990	30.32466346029981
1991	27.466007112638618
1992	29.175010966256842
1993	29.381004152534217
1994	33.669515446291356
1995	30.68087051492808
1996	43.243468137322715
1997	36.97921810499313
1998	46.68114835442358
1999	46.003253475992345
2000	42.486453151053034
2001	49.72950731597745
2002	53.018361921078935
2003	58.81829738574197
2004	54.08928482062149
2005	47.296793654330834
2006	46.27923814841836
2007	40.35060964349264
2008	45.36759656451433
2009	62.863289589281244
2010	40.6132429994333
2011	37.44686751117204
2012	36.82792726395145
2013	27.68897581636926
2014	30.2423766685491
2015	27.571233907437275
2016	27.877935586181685
2017	24.106164698640193
2018	20.53913393894995
2019	20.23631719183306
2020	22.425724145524168