Year	% of revenue
2001	11.46907177562097
2002	11.769517577488067
2003	11.305772581472116
2004	12.32611024844698
2005	12.341627049798515
2006	14.587647077608166
2007	17.237199074685172
2008	18.744210678861915
2009	19.26241307502731
2010	20.058315757115793
2011	22.34229186539672
2012	23.23426363833413
2013	24.454178828723553
2014	24.906082788304392
2015	26.855357583724043
2016	25.17086571964621
2017	24.333218249116992
2018	26.002689791241217
2019	25.44480344072195
2020	27.278984575098608
2021	25.759848385746775