Year	Percent
1960	59.752
1961	60.02
1962	60.204
1963	60.387
1964	60.57
1965	60.753
1966	60.936
1967	61.118
1968	61.3
1969	61.481
1970	61.663
1971	61.913
1972	62.232
1973	62.55
1974	62.867
1975	63.183
1976	63.498
1977	63.811
1978	64.123
1979	64.435
1980	64.745
1981	65.104
1982	65.511
1983	65.916
1984	66.319
1985	66.719
1986	67.117
1987	67.513
1988	67.906
1989	68.296
1990	68.684
1991	69.329
1992	70.223
1993	71.1
1994	71.962
1995	72.809
1996	73.64
1997	74.453
1998	75.25
1999	76.03
2000	76.795
2001	77.83
2002	79.113
2003	80.341
2004	81.514
2005	82.63
2006	83.636
2007	84.539
2008	85.402
2009	86.288
2010	87.134
2011	87.879
2012	88.588
2013	89.187
2014	89.69
2015	90.173
2016	90.635
2017	91.077