Year	Percent
1965	53.31139
1966	9.72006
1967	24.29094
1968	2.38824
1969	17.12782
1970	36.45788
1971	38.01793
1972	41.74701
1973	48.28359
1974	38.25293
1975	36.41777
1976	38.21037
1977	33.74402
1978	32.78233
1979	32.09267
1980	30.61387
1981	25.02019
1982	29.78698
1983	28.643
1984	29.80527
1985	31.34408
1986	30.33361
1987	23.08087
1988	26.59218
1989	26.85865
1990	27.55677
1991	28.40504
1992	25.40977
1993	24.18197
1994	22.78915
1995	22.47159
1996	23.35387
1997	22.44088
1998	25.1755
1999	24.14971
2000	25.82569
2001	25.69134
2002	24.7497
2003	27.37489
2004	25.30717
2005	22.09928
2006	26.1519
2007	27.1311
2008	24.51129
2009	18.3379
2010	17.04824
2011	15.10466
2012	12.80315
2013	11.60105
2014	11.91102
2015	9.81888
2016	10.60986
2017	11.72766