Year	Percent
1966	59.46802
1967	59.39323
1968	59.41691
1969	59.45802
1970	61.54199
1971	61.44105
1972	59.45946
1973	59.53125
1974	59.48749
1975	59.03962
1976	57.74932
1977	59.45051
1978	61.41183
1979	61.66087
1980	59.96625
1981	56.88873
1982	54.99847
1983	56.79156
1984	55.34928
1985	59.97497
1986	59.87088
1987	58.60136
1988	63.10685
1989	63.73193
1990	64.64796
1991	66.48112
1992	67.50428
1993	67.59345
1994	66.14374
1995	63.76733
1996	61.35045
1997	63.84531
1998	64.72775
1999	60.39355
2000	60.64504
2001	59.80754
2002	60.06809
2003	58.40268
2004	53.20312
2005	53.42991
2006	57.28149
2007	58.40976
2008	55.57069
2009	54.95841
2010	53.09228
2011	62.05252
2012	60.96123
2013	61.96077
2014	64.52106
2015	64.00358
2016	65.71237
2017	65.84823