Year	% of revenue
1990	26.019749233170103
1991	24.20675944333996
1992	23.00903774587985
1993	21.800397877984086
1994	21.73726062966569
1995	24.195119970768545
1996	23.3150894164068
1997	22.01653043394093
1998	18.97642403835341
1999	17.384974337881165
2000	14.999580342527818
2001	19.687522570447356
2002	19.230646278818096
2003	18.246185124893195
2004	18.545446615020538
2005	16.733968158391974
2006	15.168772293581206
2007	14.663222869890108
2008	14.309791531011054
2009	16.147515755223786
2010	15.673804991423543
2011	14.824628458537264
2012	15.221372669391192
2013	16.63169486087869
2014	16.721170056090912
2015	16.63159732194894
2016	15.682824620984507
2017	10.121360382253231
2018	12.879666965501361
2019	16.030555142000537
2020	15.813597111788832
2021	19.865286229934117