Year	% of revenue
1998	27.34808163164614
1999	28.854305521602562
2009	12.737957456998044
2010	13.89870719793229
2011	7.920628724804127
2012	21.14840694511483
2013	19.889832854873728
2014	15.447892448811873
2015	16.62996928429095
2016	15.653239367006137