Year	% of revenue
1998	7.209068538265605
1999	9.393781451363681
2009	6.336552659935347
2010	8.047102165600181
2012	11.38978983313861
2013	4.40493712020751
2014	7.361251822744336
2015	6.581125068348875
2016	5.1285153124443745