Year	Percent
1965	35.48284
1966	36.47044
1967	36.84491
1968	37.97338
1969	38.7307
1970	35.2964
1971	35.99636
1972	36.35932
1973	35.89495
1974	37.57774
1975	38.15043
1976	36.66913
1977	34.08983
1978	37.9391
1979	37.44385
1980	40.0967
1981	43.13162
1982	45.24699
1983	46.47094
1984	48.49525
1985	49.73128
1986	49.87832
1987	53.661
1988	53.64524
1989	55.17464
1990	54.65998
1991	54.6797
1992	54.93282
1993	53.50059
1994	53.66988
1995	54.30695
1996	55.27809
1997	56.22701
1998	56.91098
1999	57.88379
2000	58.57394
2001	58.42642
2002	59.10729
2003	59.22572
2004	60.4952
2005	60.53763
2006	60.28228
2007	59.41893
2008	58.71998
2009	60.98273
2010	59.50279
2011	57.83887
2012	58.34395
2013	59.58319
2014	59.61282
2015	60.44119
2016	60.50746
2017	59.99971