Year	% of revenue
2009	22.01483301524255
2010	21.17758146244637
2011	22.673514460082853
2012	22.701559056033112
2013	23.69199918416924
2014	24.932040138268956
2015	26.694633854299497
2016	26.51967880271319
2017	24.364700308329397
2018	26.323517446841592
2019	25.868034366238113
2020	25.625923651119088
2021	25.665296115058812