Year	Percent
1960	60.88421
1961	57.14343
1962	29.21659
1963	53.33855
1964	49.1658
1965	41.7272
1966	41.59825
1967	40.41568
1968	42.69612
1969	45.64146
1970	46.58221
1971	41.0383
1972	41.38256
1973	47.3105
1974	66.02672
1975	65.54675
1976	58.32653
1977	62.31857
1978	56.41516
1979	54.00647
1980	57.69002
1981	57.94762
1982	52.9209
1983	47.09294
1984	42.98648
1985	39.14883
1986	26.78334
1987	22.87456
1988	26.23159
1989	34.22522
1990	36.60241
1991	44.4927
1992	40.99718
1993	38.07077
1994	42.89821
1995	48.74527
1996	47.52724
1997	46.87215
1998	40.69292
1999	44.58623
2000	56.94809
2001	53.1065
2002	54.20744
2003	52.37459
2004	57.98137
2005	64.30285
2006	65.00107
2007	65.04375
2008	69.45995
2009	61.56068
2010	60.49702
2011	60.36225
2012	58.47345
2013	57.21055
2014	55.48898
2015	52.06954
2016	48.48503
2017	47.57505