Year	% of revenue
2005	20.912453217898978
2006	21.86392371903819
2007	22.655804434730733
2008	22.533768106716945
2009	22.454202994648657
2010	20.69339329861538
2011	24.288790786211827
2012	25.176172698000414
2013	23.733656768374033
2014	23.414143235014123
2015	23.613758712105312
2016	23.772720054698734
2017	23.53226295990686
2018	23.806690260649
2019	23.583202556695813
2020	22.698889394295048