Year	% of revenue
2008	1.7889352501810583
2009	1.6426968930741994
2010	1.7623503857624476
2011	1.4506137858952814
2012	1.6679600211664696
2013	1.369275469129122
2014	1.4519392607486992
2015	1.7647581483615493
2016	1.9930790031793093
2017	2.0041005709304285
2018	1.962933187131337
2019	1.8200820732959127
2020	1.3596123891450176