Year	Percent
1960	48.13698
1961	48.64914
1962	49.29153
1963	48.31527
1964	48.67741
1965	47.94998
1966	46.00237
1967	42.15936
1968	42.16612
1969	42.76551
1970	43.82704
1971	43.9816
1972	44.94407
1973	44.68826
1974	43.54982
1975	44.61093
1976	45.96035
1977	51.76761
1978	51.64193
1979	49.32801
1980	46.65607
1981	49.15182
1982	48.78499
1983	47.23605
1984	48.79435
1985	47.57453
1986	50.86455
1987	50.22315
1988	47.61287
1989	49.24215
1990	50.48469
1991	48.88142
1992	49.74484
1993	51.65484
1994	49.42005
1995	49.42301
1996	46.27143
1997	43.98419
1998	43.68318
1999	45.49412
2000	44.57949
2001	42.99815
2002	43.93206
2003	40.39867
2004	28.68793
2005	35.06783
2006	32.52469
2007	33.24858
2008	32.56867
2009	37.5115
2010	33.4128
2011	32.5931
2012	31.82447
2013	33.02001
2014	31.09101
2015	32.92
2016	32.6925
2017	33.52396