Year	Percent
1965	54.22078
1966	53.6541
1967	54.027
1968	53.41527
1969	53.64114
1970	54.01908
1971	53.4869
1972	52.94841
1973	52.90864
1974	53.37782
1975	53.45773
1976	52.60242
1977	52.81225
1978	52.95989
1979	53.0938
1980	53.16835
1981	53.26789
1982	53.63937
1983	54.15391
1984	54.61747
1985	54.47888
1986	54.29903
1987	54.17481
1988	53.96057
1989	54.26015
1990	54.33308
1991	54.68455
1992	54.70572
1993	55.25427
1994	55.82719
1995	56.18768
1996	56.25846
1997	56.29901
1998	56.56573
1999	56.83377
2000	57.38774
2001	53.92243
2002	53.47133
2003	53.99148
2004	54.07625
2005	55.35758
2006	55.81135
2007	56.10233
2008	57.10148
2009	57.98829
2010	58.51774
2011	58.01319
2012	58.58927
2013	59.20404
2014	59.21494
2015	60.40152
2016	61.4756
2017	62.13798