Year	Percent
1960	53.73888
1961	51.29735
1962	52.00457
1963	51.70508
1964	56.30285
1965	51.7886
1966	50.62376
1967	50.10917
1968	55.72721
1969	57.92866
1970	61.73269
1971	57.89538
1972	54.8567
1973	55.96806
1974	64.8356
1975	65.82281
1976	52.01681
1977	50.105
1978	65.70843
1979	74.71029
1980	76.80797
1981	82.13996
1982	65.21871
1983	61.11689
1984	79.75339
1985	79.84866
1986	56.66954
1987	59.1423
1988	59.3212
1989	63.99589
1990	67.20055
1991	71.91949
1992	77.11931
1993	59.25887
1994	63.40495
1995	64.91977
1996	59.01194
1997	53.90995
1998	49.60506
1999	46.76
2000	51.5283
2001	49.90185
2002	47.93603
2003	51.25993
2004	52.62547
2005	55.96849
2006	63.82437
2007	71.32667
2008	79.71729
2009	52.99762
2010	49.67408
2011	55.83335
2012	54.343
2013	54.53787
2014	52.43668
2015	44.09435
2016	42.46222
2017	47.16235