Year	% of total
1990	77.85069873072608
1995	76.06867991723124
2000	74.73167813267301
2005	74.86473006556709
2010	72.28995248197691
2011	75.52426519573066
2012	67.78458847577846
2013	64.64708462144334
2014	59.379626576468745
2015	58.76736253656053
2016	52.77011158135952
2017	52.807788243848194