Year	Percent
1960	54.37991
1961	53.66816
1962	57.16955
1963	60.0912
1964	56.94486
1965	58.23361
1966	60.32293
1967	58.37247
1968	56.68867
1969	59.88081
1970	61.58556
1971	60.72451
1972	61.57357
1973	60.20035
1974	82.5507
1975	80.83484
1976	74.22053
1977	71.71154
1978	66.79261
1979	72.91372
1980	72.47063
1981	71.43372
1982	59.97529
1983	45.99755
1984	47.3699
1985	48.61737
1986	50.21841
1987	51.22707
1988	47.85618
1989	57.33903
1990	64.30026
1991	75.8943
1992	78.52249
1993	75.62056
1994	77.56698
1995	80.05828
1996	84.71969
1997	88.35544
1998	83.61561
1999	69.83255
2000	71.97836
2001	67.96293
2002	64.21205
2003	60.35333
2004	65.88491
2005	71.19352
2006	71.72225
2007	78.11174
2008	88.6092
2009	69.16632
2010	78.23204
2011	84.25716
2012	82.8673
2013	72.47229
2014	63.73312
2015	52.15155
2016	45.90367