Year	% of revenue
2010	4.326115409442442
2012	4.85322794989012
2013	5.131569475452839
2014	4.11351584475481
2015	5.685372304579954
2016	6.149528215889506
2017	6.079156114762082
2018	9.007485428885067
2019	6.497910167034822
2020	7.5589984540768205
2021	8.304231506299542