Year	Percent
1960	85.66332
1961	86.91327
1962	86.70064
1963	87.32993
1964	87.08073
1965	45.32147
1966	41.16272
1967	40.80982
1968	41.1454
1969	39.84559
1970	39.83439
1971	39.94839
1972	41.46833
1973	39.96674
1974	35.79437
1975	34.89289
1976	39.83905
1977	40.62915
1978	44.02438
1979	43.01848
1980	43.91495
1981	46.34649
1982	47.73983
1983	47.08884
1984	45.48129
1985	59.43077
1986	49.87149
1987	60.18675
1988	51.56855
1989	47.03081
1990	47.66578
1991	48.02107
1992	48.98473
1993	50.44228
1994	51.03802
1995	51.60128
1996	51.77057
1997	52.8605
1998	51.95731
1999	53.00056
2000	54.21923
2001	56.28742
2002	55.99253
2003	57.81125
2004	57.48967
2005	57.89259
2006	57.7409
2007	56.92493
2008	59.16883
2009	61.02449
2010	61.43374
2011	61.90504
2012	62.56696
2013	61.5691
2014	61.09421
2015	61.43917
2016	62.27422
2017	61.99726