Year	% of total
1990	71.834764742427
1995	72.0654884032298
2000	74.4109182040611
2005	76.1037397761331
2010	79.2033285915654
2011	80.8430040541272
2012	80.0440392641734
2013	79.6849229991942
2014	79.0823214593167
2015	81.0889013733115
2016	79.7089799023927
2017	80.5605926692777