Year	% of total
1990	85.1898043783997
1995	84.8449210770766
2000	78.5834064788399
2005	78.371915039265
2010	79.1652486902008
2011	82.1177520198289
2012	78.1361802745036
2013	76.7964524745358
2014	72.8580129105126
2015	76.2006217852119
2016	72.1724486423162
2017	72.2426656411247