Year	% of total
1990	7.06209645508846
1995	6.04620150469012
2000	6.9621746751795
2005	6.81853058374079
2010	6.86900502194074
2011	7.34183305759848
2012	6.21506543239509
2013	5.2455052220905
2014	4.43229859266157
2015	4.56635190773633
2016	3.54533901106235
2017	3.65969564424943