Year	% of revenue
2010	29.913354736171456
2012	34.281449961959495
2013	31.53227729856501
2014	36.29177143237658
2015	36.25416527274747
2016	39.05936414415581
2017	35.293046407578046
2018	37.914087765659126
2019	36.959877058441855
2020	36.19831750561488