Year	% of revenue
2011	26.706986277417016
2012	28.615595685431934
2014	22.555464556495167
2015	18.673594119120974
2016	19.690933037047984
2017	20.028776079927816
2018	20.172863519103174
2019	20.64874847505758
2020	17.429271656082243
2021	23.612079529675064