Year	% of revenue
2012	21.12388843150709
2013	24.52663656567995
2014	25.12164655032503
2015	27.31487676804481
2016	22.64316753498395
2017	24.364700308329397
2018	28.760293631424673
2019	29.404854962064324
2020	35.596268671015565
2021	23.924434496564295