Year	Percent
1960	46.619
1961	46.793
1962	46.906
1963	47.02
1964	47.134
1965	47.248
1966	47.362
1967	47.476
1968	47.59
1969	47.704
1970	47.809
1971	47.869
1972	47.929
1973	47.989
1974	48.049
1975	48.109
1976	48.169
1977	48.229
1978	48.289
1979	48.349
1980	48.425
1981	48.591
1982	48.756
1983	48.922
1984	49.088
1985	49.372
1986	49.905
1987	50.439
1988	50.972
1989	51.505
1990	52.037
1991	52.554
1992	53.038
1993	53.521
1994	54.004
1995	54.486
1996	54.967
1997	55.449
1998	55.93
1999	56.411
2000	56.891
2001	57.368
2002	57.898
2003	58.446
2004	58.993
2005	59.536
2006	60.077
2007	60.616
2008	61.154
2009	61.687
2010	62.218
2011	62.746
2012	63.272
2013	63.793
2014	64.312
2015	64.828
2016	65.341
2017	65.85