Year	Percent
1960	30.6325
1961	30.74133
1962	28.82844
1963	29.27839
1964	35.78889
1965	34.92132
1966	33.00064
1967	40.34924
1968	37.86182
1969	37.2307
1970	37.03316
1971	41.48749
1972	24.53312
1973	22.38298
1974	29.9387
1975	35.35631
1976	32.07536
1977	28.89079
1978	28.34818
1979	19.96671
1980	26.05278
1981	26.39222
1982	25.73031
1983	25.47051
1984	20.00102
1985	14.32428
1986	8.46124
1987	16.03313
1988	16.38498
1989	23.13348
1990	31.74903
1993	61.97796
1994	46.224
1995	33.43939
1996	32.11274
1997	28.59659
1998	24.88372
1999	26.74784
2000	38.90532
2001	33.41616
2002	35.02922
2003	38.1309
2004	38.7664
2005	42.52245
2006	44.23
2007	38.20578
2008	42.12786
2009	31.2994
2010	34.2292
2011	33.20649
2012	26.90007
2013	28.17625
2014	32.17679
2015	27.18501
2016	26.97047
2017	31.62588