Year	Percent
1965	56.88806
1966	57.67059
1967	56.87048
1968	57.04847
1969	57.06677
1970	52.46164
1971	53.52796
1972	54.28335
1973	53.75107
1974	53.02333
1975	52.61309
1976	53.72619
1977	52.7403
1978	53.02265
1979	52.88077
1980	52.95698
1981	53.5457
1982	53.32724
1983	52.14242
1984	51.17899
1985	49.55493
1986	50.41945
1987	47.25646
1988	55.11439
1989	57.65495
1990	58.31414
1991	58.94816
1992	59.63406
1993	58.02197
1994	58.4621
1995	58.73312
1996	57.18006
1997	56.85997
1998	56.94507
1999	57.00996
2000	57.80234
2001	58.38606
2002	58.84521
2003	60.42439
2004	59.38822
2005	60.00567
2006	58.96626
2007	59.18534
2008	59.52232
2009	60.72183
2010	60.36282
2011	59.91247
2012	59.99725
2013	61.10639
2014	60.19384
2015	61.02596
2016	61.05372
2017	60.94543