Year	% of revenue
2010	36.234905480534316
2011	30.382986339458057
2012	27.083857239956405
2013	27.99174148544093
2014	23.600493060770212
2015	23.754347522073598
2016	20.59052098602107
2017	23.232375999843665
2018	21.11698810993915
2019	21.937256429805185
2020	20.903564606675758
2021	18.573356339027548