Year	% of revenue
2006	14.194838632969521
2007	14.52615233106765
2008	15.453390231786173
2009	16.18501208702659
2010	17.006360231199864
2011	16.208236634078737
2012	16.434938125984417
2013	16.055992269723955
2014	17.04176089039569
2015	17.24016915021604
2016	17.467566649024626
2017	17.580914235294383
2018	17.739220542379734
2019	17.87982856772585
2020	16.843030963791797
2021	15.672947834214982