Year	Percent
1960	48.66813
1961	52.88138
1962	41.64196
1963	47.24012
1964	52.3332
1965	54.59293
1966	48.81807
1967	46.02353
1968	56.4894
1969	53.24816
1970	50.01814
1971	50.27298
1972	50.20101
1973	49.84509
1974	56.38055
1975	44.57618
1976	42.31344
1977	45.76296
1978	46.68916
1979	46.48727
1980	59.14494
1981	42.87647
1982	31.57419
1983	28.03726
1984	26.66736
1985	32.79299
1986	56.30568
1987	38.07174
1988	24.83215
1989	34.40609
1990	44.17799
1991	39.48812
1992	43.38248
1993	34.46875
1994	29.0597
1995	20.09742
1996	27.39603
1997	12.93786
1998	15.17009
1999	12.99701
2000	25.47675
2001	19.3495
2002	24.96949
2003	28.55045
2004	29.34368
2005	30.48693
2006	32.89125
2007	31.96233
2008	29.9269
2009	30.60296
2010	43.10518
2011	70.22036
2012	71.68584
2013	75.13533
2014	62.21568
2015	48.40362
2016	43.37954
2017	49.52967