Year	Percent
1960	38.36349
1961	39.03532
1962	43.07351
1963	42.76208
1964	46.53706
1965	48.90543
1966	48.50877
1967	47.82284
1968	49.71302
1969	50.9354
1970	55.63396
1971	53.39075
1972	52.79217
1973	52.31157
1974	69.60509
1975	60.54986
1976	56.50855
1977	60.19997
1978	57.63496
1979	57.76704
1980	52.61364
1981	84.49554
1982	67.48199
1983	46.80049
1984	45.71271
1985	43.2387
1986	41.42102
1987	43.50183
1988	43.80121
1989	45.61341
1990	46.43776
1991	48.47259
1992	50.19585
1993	64.37882
1994	63.81906
1995	65.04554
1996	69.11518
1997	73.23094
1998	86.22054
1999	90.85195
2000	81.8555
2001	72.83187
2002	75.44474
2003	80.04947
2004	78.62737
2005	84.45403
2006	87.37944
2007	83.34395
2008	81.25749
2009	66.02304
2010	61.76159
2011	63.00568
2012	62.45351
2013	59.51691
2014	56.86452
2015	46.90884
2016	43.43979
2017	44.8198