Year	Percent
1960	20.45333
1961	19.45956
1962	30.4896
1963	36.4729
1964	38.1526
1965	36.00822
1966	29.8893
1967	30.47946
1968	30.38584
1969	32.07549
1970	34.73683
1971	32.58173
1972	28.30918
1973	31.62252
1974	53.22918
1975	35.88808
1976	40.37715
1977	45.58499
1978	43.72144
1979	47.41176
1980	60.01665
1981	58.02104
1982	55.26761
1983	57.94545
1984	61.62754
1985	56.78822
1986	39.8337
1987	41.73431
1988	40.62215
1989	48.5242
1990	51.77736
1991	41.63459
1992	40.6921
1993	42.83637
1994	58.51702
1995	64.70457
1996	68.45821
1997	75.59664
1998	76.27763
1999	72.29007
2000	80.29715
2001	77.42003
2002	81.51643
2003	80.81237
2004	80.52979
2005	84.15817
2006	84.15968
2007	78.52948
2008	75.1515
2009	70.41798
2010	85.11967
2011	87.28305
2012	83.77515
2013	76.53246
2014	72.98675
2015	69.27557
2016	57.08428
2017	79.76307