Year	% of revenue
2012	19.899790073203206
2013	19.700081108554677
2014	20.140741225925876
2015	23.424202091476662
2016	21.98524240986785
2017	22.95125379107761
2018	24.15419474228239
2019	23.078694421340863
2020	24.69792976675691
2021	25.201103900125982