Year	Percent
1963	30.64202
1964	32.91367
1965	36.64384
1966	39.34837
1967	40.06116
1968	39.78052
1969	42.68675
1970	42.17935
1971	46.76734
1972	46.11558
1973	46.7928
1974	47.66667
1975	47.72405
1976	47.40976
1977	51.35583
1978	53.51752
1979	52.04177
1980	51.15381
1981	53.1528
1982	53.53903
1983	55.89091
1984	56.08061
1985	55.63198
1986	53.54368
1987	50.57214
1988	53.07439
1989	47.64693
1990	48.93405
1991	48.69947
1992	47.74438
1993	46.74432
1994	45.92644
1995	47.64542
1996	48.22289
1997	49.221
1998	50.26886
1999	50.47447
2000	53.08584
2001	53.72752
2002	53.41507
2003	53.23906
2004	52.51923
2005	56.83386
2006	56.32179
2007	57.63075
2008	57.46719
2009	58.48383
2010	57.488
2011	58.15737
2012	57.99604
2013	56.87172
2014	58.55585
2015	58.82679
2016	56.42791