Year	% of revenue
2010	18.780860620409648
2012	21.390896466329306
2013	21.90259630069574
2014	20.826436158394976
2015	23.424202091476662
2016	22.429646207724335
2017	22.366963421431898
2018	24.15419474228239
2019	23.535058220415124
2020	24.357188749210913
2021	25.201103900125982