Year	Percent
1966	36.43105
1967	33.25279
1968	29.78654
1969	38.41761
1970	42.25832
1971	46.36363
1972	44.51117
1973	33.72982
1974	44.42722
1975	45.25764
1976	46.05697
1977	47.5693
1978	54.34523
1979	51.54267
1980	49.26233
1981	56.64859
1982	66.34232
1983	66.18312
1984	64.03556
1985	63.59139
1986	66.27057
1987	63.77605
1988	64.4258
1989	60.75165
1990	54.95566
1991	57.5377
1992	60.44571
1993	59.99344
1994	55.81423
1995	57.72894
1996	57.76428
1997	59.98127
1998	64.68173
1999	63.04702
2000	56.35099
2001	59.06081
2002	60.12222
2003	52.79518
2004	49.31093
2005	45.09665
2006	43.12793
2007	45.45905
2008	41.40097
2009	54.80882
2010	49.33849
2011	46.08454
2012	47.46939
2013	50.05244
2014	50.68377
2015	59.60103
2016	61.98709
2017	59.64591