Year	% of total
1960	94.66844186778162
1961	94.7218399639619
1962	94.80033760389401
1963	95.00987242519327
1964	95.02844148731127
1965	95.1230156346565
1966	95.1875986991345
1967	95.19445704043522
1968	95.11948011729716
1969	95.0177460051259
1970	94.99900158080183
1971	94.70438589999839
1972	94.41601433653767
1973	93.9495822215232
1974	93.11362845744478
1975	92.27313951318033
1976	92.1491037983508
1977	91.54944918991177
1978	90.81850213861648
1979	90.84675366728105
1980	90.38192495094582
1981	89.73927308978534
1982	88.9808758803444
1983	88.25559693919081
1984	87.7312266179829
1985	87.03648334140799
1986	86.25047547734472
1987	86.03335706144897
1988	85.78279114912581
1989	85.88501205807718
1990	85.16273728652847
1991	84.37540827588487
1992	84.37671795095791
1993	84.76258577426297
1994	84.46847061086608
1995	84.15351636468152
1996	84.2655792958048
1997	85.26775456348113
1998	85.06429696720204
1999	84.76685524014316
2000	84.89943074538446
2001	85.3192645548378
2002	85.14040000199232
2003	85.26115787563803
2004	84.97949359569645
2005	84.9415203373464
2006	84.46896565563432
2007	84.48749680107309
2008	83.91108998420506
2009	83.17238741846877
2010	83.2145451651991
2011	82.7184953271957
2012	82.44126709982895
2013	81.85935660486248
2014	81.97940165349048
2015	81.5022869331202