Year	% of revenue
2010	30.476864510554975
2012	35.09803971770535
2013	33.88852999685861
2014	37.062117114500055
2015	38.883894619301
2016	41.11638155497215
2017	36.67973884935672
2018	38.614079437343484
2019	38.58031231013962
2020	37.777253891209625
2021	39.753074514708814