Year	% of revenue
2001	5.439002838322712
2002	5.839266576103651
2003	5.606190225497938
2004	5.667414764806172
2005	4.774093213886504
2006	4.555298390277664
2007	4.812546920233804
2008	3.7192260566137185
2009	4.395683643470297
2010	4.096387096219415
2011	4.610888486178821
2012	4.442920520109416
2013	4.610593121437645
2014	4.604235285031368
2015	4.902597032938257
2016	5.428844813820873
2017	6.470351017186199
2018	5.715295658048579
2019	5.979690049787442