Year	% of revenue
2005	15.810658596123314
2006	16.077885294834548
2007	16.33768424511869
2008	15.832502700766234
2009	14.81425721987177
2010	14.479944426846828
2011	17.429930180091947
2012	16.908241029209343
2013	16.015892000656308
2014	17.418812966849632
2015	15.145090180811735
2016	16.78568492581533
2017	15.518817927072398
2018	15.608757013055577
2019	14.812930995600219
2020	15.030021997579254