Year	% of revenue
2011	19.30578126992975
2012	18.866809800491602
2013	23.325931308595663
2014	24.68724592810955
2015	24.236828094111605
2016	24.443032250835227
2017	24.78279613429843
2018	20.636081233474464
2019	21.976497493475243
2020	15.810808951244995