Year	% of revenue
2003	17.721328964688468
2004	17.776825872777895
2005	16.920253332411544
2006	18.156172167323792
2007	17.187678133839096
2008	19.320112548247405
2009	19.71838478437193
2010	20.17281457206006
2011	20.554102717753555
2012	20.591991774732165
2013	20.032710942909024
2014	20.974313760069755
2015	23.114255228592313
2016	22.429646207724335
2017	22.48427672955975
2018	23.538275906239832
2019	23.350618398991195
2020	24.434007903702202
2021	24.88097198274857