Year	% of total
1960	99.92205857630788
1965	99.92680008182006
1966	99.93043175685561
1967	99.78853643649973
1968	99.9009190916956
1970	99.8288252764552
1974	99.89391042234143
1975	95.91331198678826
1976	94.81361982669216
1977	93.22929388313872
1978	93.45493634077086
1979	93.96135351450819
1980	93.31781526050695
1981	92.03893616726549
1982	89.88439231104091
1983	84.38106338257546
1984	82.6687776127733
1985	79.15095240311723
1986	77.06576913373777
1987	76.44918323624755
1988	76.08510889255467
1989	77.01784999068049
1990	75.81586996057928
1991	76.39700682697494
1992	75.93220101989697
1993	75.93501515540471
1994	77.64937481182595
1995	77.40569753026469
1996	77.64448379496281
1997	75.8983187385392
1998	77.04852704579567
1999	75.79014289912543
2000	75.85408639607883
2001	75.62829262757859
2002	74.4701814763315
2003	75.23284587397795
2004	75.01945859352328
2005	74.76394898443138
2006	73.94251148624052
2007	72.66654993028439
2008	73.3936320880596
2009	72.64002311671355
2010	72.79361703721048
2011	70.25449592628259
2012	71.11571411240695
2013	70.82030579611401
2014	72.65250483564859
2015	75.87078435368242