Year	% of revenue
2011	6.705131614285537
2012	9.818539551768193
2014	7.843338183587877
2015	9.316339010764906
2016	9.34873096438907
2017	7.014927223837691
2018	6.219298637228716
2019	6.557549527101446
2020	7.911935786730598
2021	7.231333935382148