Year	Percent
1960	45.38169
1961	45.22535
1962	43.4447
1963	44.46503
1964	45.73582
1965	45.33546
1966	45.61833
1967	47.14196
1968	45.70975
1969	46.50863
1970	48.06322
1971	45.4632
1972	44.10422
1973	48.87834
1974	54.16115
1975	51.51208
1976	53.06117
1977	52.42998
1978	48.10364
1979	51.29164
1980	55.07346
1981	53.25595
1982	52.78768
1983	51.10402
1984	52.80709
1985	54.33154
1986	48.78817
1987	46.83113
1988	44.8046
1989	49.42622
1990	51.1538
1991	48.9684
1992	46.68596
1993	46.28415
1994	48.76763
1995	49.3071
1996	52.14112
1997	52.21365
1998	50.51723
1999	49.08125
2000	55.13215
2001	52.95648
2002	48.3757
2003	47.37698
2004	49.57718
2005	51.5828
2006	53.98261
2007	54.01673
2008	56.65443
2009	48.04383
2010	48.46701
2011	50.35634
2012	48.65673
2013	46.95865
2014	46.88934
2015	46.60287
2016	43.69798
2017	46.31757