Year	Percent
1960	33.91758
1961	31.56536
1962	30.60173
1963	38.13336
1964	30.75439
1965	33.87387
1966	34.9338
1967	37.87425
1968	45.54183
1969	45.58652
1970	47.59775
1971	45.57563
1972	51.24425
1973	47.8584
1974	63.35755
1975	62.28374
1976	62.35572
1977	58.25848
1978	57.82641
1979	61.75923
1980	60.42911
1981	58.40877
1982	60.63588
1983	56.83665
1984	59.6967
1985	66.52782
1986	47.50064
1987	48.84822
1988	35.94957
1989	41.72969
1990	42.99642
1991	44.61223
1992	43.31982
1993	45.24836
1994	52.61903
1995	52.36345
1996	55.36597
1997	53.65218
1998	43.14178
1999	48.81574
2000	56.2552
2001	47.71007
2002	47.31567
2003	47.03917
2004	51.50054
2005	59.92236
2006	59.46632
2007	57.22221
2008	61.742
2009	50.44591
2010	55.19089
2011	60.88142
2012	58.82279
2013	56.60906
2014	52.72098
2015	48.1851
2016	45.16665
2017	44.63539