Year	% of revenue
1993	5.794349939246659
1994	5.338478855121402
1995	4.515346580837765
1996	7.4607214956552275
1997	7.512586532410322
1998	6.899595439499816
1999	5.976859504132231
2000	5.161290322580645
2005	35.607266239194836
2006	35.15406054468454
2007	42.56300672873606
2008	35.96415755036579
2009	43.77541480146324
2010	38.27477550795004
2011	30.721880038345624
2012	32.322132857703345
2013	44.314526540965346
2014	48.69310389026893
2015	43.915982082854256
2016	48.14902524037382
2017	52.14506730709113
2018	47.688940974216415
2019	49.59719437353656
2020	47.34322002648626