Year	Percent
1965	27.86856
1966	29.48428
1967	33.01709
1968	33.49657
1969	26.25401
1970	24.98067
1971	33.40697
1972	28.47429
1973	32.37337
1974	36.34655
1975	35.47882
1976	28.77937
1977	30.02875
1978	24.79891
1979	25.06738
1980	27.05296
1981	26.79272
1982	28.04198
1983	21.02082
1984	23.17157
1985	20.76971
1986	18.43148
1987	20.70359
1988	20.83554
1989	18.80489
1990	18.97692
1991	20.03111
1992	18.10413
1993	16.91152
1994	16.00557
1995	16.34202
1996	18.95001
1997	21.40943
1998	25.70645
1999	23.34946
2000	24.60241
2001	22.73963
2002	19.62182
2003	21.15474
2004	24.59947
2005	29.33351
2006	36.00031
2007	29.79563
2008	25.8239
2009	14.78928
2010	13.78089
2011	15.40341
2012	16.01548
2013	15.36555
2014	17.28416
2015	19.13844
2016	21.47411
2017	22.16805