Year	% of revenue
2008	14.911452473229888
2009	16.608794118071284
2010	13.033455254786245
2011	17.01498577433315
2012	17.446136591191934
2013	13.801208241660873
2014	15.910805521865711
2015	17.11286909223387
2016	18.117290933921065
2017	18.937153021085773
2018	17.617083758537895
2019	17.6430168658547
2020	19.533762087473338
2021	18.975064226950742