Year	% of revenue
2008	71.55837796429813
2009	71.50697674656756
2010	71.74320448635125
2011	70.6493583698481
2012	68.75989714434398
2013	69.89414267525859
2014	69.74264903292081
2015	70.62813919496263
2016	71.37323627561952
2017	74.11651773872217
2018	71.5629553750487
2019	70.80197851182872
2020	75.77933869338518