Year	% of revenue
2008	18.125446017208468
2009	18.205976359104774
2010	17.841570893778737
2011	21.712598241791287
2012	21.889175527233423
2013	25.19505051557015
2014	24.169428455737226
2015	26.951339234533894
2016	24.650234107218967
2017	25.151603299757948
2018	24.71564696644899
2019	21.133478036222794
2020	14.151083697957842