Year	% of revenue
1997	47.67449501794852
1998	29.883981037134806
1999	0.18124641037953468
2010	2.6673522926771236
2011	2.2717413085752827
2012	2.5866475269027083
2013	2.698877522983673
2014	2.8692454180945943
2015	4.178768646170507
2016	3.9592644066908966
2017	3.1045448681684493
2018	3.259493364456947