Year	% of revenue
2006	8.737159203710998
2007	8.275726773375277
2008	6.9348782697100955
2009	6.260529173513649
2010	6.175251837821051
2011	6.0104613292531175
2012	5.868787909873886
2013	5.641286937442557
2014	5.967217873263703
2015	5.810116062187875
2016	6.381246586407016
2017	6.122909150705465
2018	5.816218707382726
2019	5.766221911990865
2020	6.023183842945887
2021	5.598123658235918