Year	% of revenue
2009	32.14649632428031
2010	35.72622267867428
2011	30.382986339458057
2012	27.7705180021236
2013	30.40513369871147
2014	24.076650195183575
2015	23.754347522073598
2016	20.260979374245057
2017	23.293255695574967
2018	21.370205045379848
2019	23.05123626149021
2020	22.418684502853388
2021	19.004756806225174