Year	Percent
1960	22.99162
1961	27.0472
1962	31.08757
1963	29.54332
1964	22.62492
1965	21.62159
1966	21.0536
1967	23.29833
1968	21.94422
1969	23.50614
1970	24.96127
1971	24.60692
1972	49.20603
1973	46.33999
1974	59.28841
1975	60.39778
1976	77.89496
1977	73.57381
1978	64.84561
1979	59.78753
1980	66.65643
1981	74.94533
1982	84.70313
1983	76.30288
1984	73.13771
1985	80.78802
1986	79.31299
1987	66.58464
1988	63.0286
1989	56.7405
1990	60.73168
1991	40.94122
1992	28.89429
1993	29.99384
1994	40.52138
1995	46.23223
1996	45.30847
1997	42.50682
1998	38.9947
1999	36.6169
2000	45.3032
2001	46.62997
2002	42.2672
2003	46.81229
2004	66.60892
2005	82.48062
2006	51.74105
2007	58.13394
2008	67.04051
2009	56.75961
2010	61.17551
2011	62.48701
2012	79.46993
2013	72.04079
2014	65.77791
2015	72.2603
2016	63.37795
2017	66.09312