Year	% of total
1960	89.33975945488103
1961	89.61421351964283
1962	90.24593900972727
1963	90.48215583075728
1964	90.86472001675193
1965	91.11421493492654
1966	91.26485868739802
1967	91.43384413892046
1968	91.72587447833783
1969	92.1627322655627
1970	92.61986407562019
1971	58.550548884245565
1972	59.301829803831545
1973	60.42576353563648
1974	60.87894259129959
1975	62.150387416510924
1976	62.99207080736011
1977	64.3640929950993
1978	65.69862741424517
1979	66.0432604069311
1980	66.08994435714519
1981	65.84130400263558
1982	66.43728456329143
1983	66.44879199978509
1984	66.82741013906833
1985	67.17153432937887
1986	67.63386034352544
1987	68.28452694689302
1988	68.74368769924644
1989	68.91048089833602
1990	77.61569834979281
1991	77.2016120448625
1992	76.60944011908613
1993	76.44456755143433
1994	75.94062142351116
1995	76.36655133881207
1996	76.40090017890209
1997	76.32929967539928
1998	76.12345522026301
1999	76.2170071122191
2000	76.27889906201382
2001	76.50362350338284
2002	76.7853124024198
2003	77.62910919922929
2004	78.37299622024065
2005	78.92780643724409
2006	79.4630272336375
2007	79.84503241203626
2008	80.02918161966237
2009	80.06400295201742
2010	80.62783612874328
2011	80.9960334230629
2012	80.87730478112191
2013	80.64154593947805
2014	80.84743149946114
2015	88.08939589093121