Year	% of total
1960	93.76106289961706
1961	93.62560708361822
1962	93.8137719087475
1963	94.19565521172737
1964	94.56969870151079
1965	94.60694039258378
1966	94.14087001402063
1967	94.360653470378
1968	94.5036046655083
1969	94.79038968631667
1970	94.22245621200553
1971	94.50827106402176
1972	93.98593856819514
1973	94.48097835125245
1974	94.26894850954068
1975	93.43752727375431
1976	93.90027924065562
1977	92.64788859849946
1978	92.4979578046907
1979	92.51077328825981
1980	91.78282081652107
1981	89.77261625613833
1982	89.0650840232683
1983	87.73915452001401
1984	85.78693341034746
1985	84.28127353475128
1986	83.58832258718235
1987	83.2213738436599
1988	82.28146015489828
1989	81.86885669516305
1990	80.88078633257244
1991	80.36281507952152
1992	79.7137439510754
1993	79.01289444250278
1994	78.88216124230229
1995	78.90350031621875
1996	78.71049398092532
1997	78.16503900016018
1998	78.27947760334911
1999	77.77490589079814
2000	77.36916220422293
2001	77.23596397750461
2002	77.0898352452003
2003	77.06382129746204
2004	76.67393906365079
2005	76.40953636931101
2006	76.12642814874452
2007	75.72293357523994
2008	74.83150619053478
2009	73.80373833091633
2010	73.18514518020581
2011	72.82949596336267
2012	71.86365252935241
2013	71.0335864186312
2014	69.67524016157651
2015	69.88602617063854