Year	Percent
1965	59.80392
1966	62.68085
1967	61.96809
1968	60.32934
1969	60.57692
1970	64.18564
1971	64.07927
1972	61.89631
1973	61.52854
1974	59.00959
1975	59.99082
1976	62.8239
1977	60.53013
1978	59.69324
1979	63.79644
1980	61.8046
1981	60.35756
1982	60.1794
1983	59.39774
1984	60.4807
1985	62.71805
1986	58.36688
1987	58.61979
1988	60.92643
1989	62.33314
1990	58.94253
1991	60.04395
1992	56.01636
1993	57.15683
1994	55.59273
1995	56.90638
1996	59.07818
1997	61.37544
1998	59.31152
1999	60.36503
2000	61.95266
2001	61.85871
2002	60.58151
2003	61.12698
2004	60.99728
2005	60.93729
2006	59.70351
2007	58.37532
2008	56.85933
2009	57.70373
2010	57.62815
2011	57.6028
2012	58.69295
2013	58.8548
2014	58.4057
2015	58.32983
2016	58.84037
2017	58.75561