Year	Percent
1960	46.139
1961	47.122
1962	48.099
1963	49.078
1964	50.059
1965	51.037
1966	52.016
1967	52.993
1968	53.97
1969	54.94
1970	55.909
1971	56.894
1972	57.879
1973	58.855
1974	59.826
1975	60.789
1976	61.745
1977	62.689
1978	63.625
1979	64.551
1980	65.468
1981	66.37
1982	67.262
1983	68.142
1984	69.01
1985	69.862
1986	70.703
1987	71.529
1988	72.342
1989	73.139
1990	73.922
1991	74.69
1992	75.444
1993	76.181
1994	76.903
1995	77.61
1996	78.302
1997	79.048
1998	79.781
1999	80.496
2000	81.192
2001	81.553
2002	81.88
2003	82.203
2004	82.521
2005	82.834
2006	83.143
2007	83.448
2008	83.749
2009	84.044
2010	84.335
2011	84.631
2012	84.923
2013	85.209
2014	85.492
2015	85.77
2016	86.042
2017	86.309