Year	% of total
1960	94.37437441752736
1961	94.327080864299
1962	94.43069422475692
1963	94.62430720183067
1964	94.7252776746792
1965	94.68512727807686
1966	94.58867052887035
1967	94.72457672863032
1968	94.7248890604034
1969	94.77968151418906
1970	94.6567912919222
1971	94.42032995288872
1972	94.11157949663021
1973	94.09435949551893
1974	93.39946619980435
1975	92.57874277884818
1976	92.59162623535273
1977	91.88540549278792
1978	91.20426394009455
1979	91.17403506785415
1980	90.53478658446795
1981	89.42133737582674
1982	88.53099942694408
1983	87.50957820759699
1984	86.48113110890726
1985	85.34984388456459
1986	84.67126619316811
1987	84.28843260806315
1988	83.97584858490815
1989	83.84360334646192
1990	83.8884753494929
1991	83.34238931791904
1992	83.09098246267578
1993	82.84818725306587
1994	82.7284262869155
1995	82.3809318275722
1996	82.26179146111458
1997	82.55210663497219
1998	82.27421132153314
1999	82.19224356037138
2000	82.1217873764684
2001	82.37188412410131
2002	82.36047136161302
2003	82.60721409014695
2004	82.20346184556671
2005	81.89351362806386
2006	81.52179968598625
2007	81.74777789146533
2008	81.21909380258406
2009	80.3324991135654
2010	80.21912560135246
2011	80.58865992718636
2012	80.64624889056313
2013	80.13653900155452
2014	79.66363017588768
2015	78.99552189517414