Year	% of revenue
1998	17.34456621624122
1999	14.528396747277483
2009	4.640419842758511
2010	5.477893132863019
2011	4.203168573417624
2012	6.462439270844141
2013	4.99424391239089
2014	5.86381976938258
2015	5.693598875592204
2016	5.8543464322808205