Year	% of revenue
1997	16.74128720401221
2002	13.020771911915887
2003	12.633678513543042
2004	12.029794028120179
2005	9.63758121302312
2006	9.311947777924305
2007	8.762149058100484
2008	7.973155495525916
2009	8.14767661052181
2010	8.437186178491435
2011	8.05414928558724
2012	9.994100416560379
2014	11.148808092474367