Year	Percent
1960	67.14363
1961	67.50377
1962	20.81865
1963	36.82552
1964	29.43976
1965	25.83308
1966	24.65357
1967	21.63177
1968	24.18725
1969	28.07076
1970	29.15267
1971	27.66378
1972	25.72687
1973	31.58976
1974	35.48978
1975	42.9656
1976	37.11867
1977	41.74032
1978	40.16873
1979	32.86575
1980	30.33846
1981	30.87774
1982	28.99807
1983	25.80231
1984	27.46637
1985	26.74219
1986	23.17195
1987	18.41211
1988	22.60372
1989	28.51406
1990	24.93703
1991	23.59976
1992	23.86949
1993	23.13894
1994	26.05371
1995	28.99623
1996	23.9447
1997	21.3376
1998	22.5161
1999	22.779
2000	20.78863
2001	22.01686
2002	25.62963
2003	23.87594
2004	25.6482
2005	24.0734
2006	21.91933
2007	24.86996
2008	28.71118
2009	35.95268
2010	31.42211
2011	28.68532
2012	28.51443
2013	30.40093
2014	31.92666
2015	36.54646
2016	35.27028
2017	36.33594