Year	Percent
1960	13.00357
1961	14.34946
1962	15.04865
1963	18.04463
1964	17.93546
1965	15.04565
1966	13.94854
1967	15.54404
1968	16.84355
1969	15.40494
1970	16.40913
1971	17.18122
1972	16.66667
1973	17.02287
1974	20.72543
1975	22.70454
1976	19.14223
1977	16.62837
1978	15.21413
1979	19.35564
1980	23.14618
1981	23.65264
1982	24.41799
1983	21.23991
1984	16.46824
1985	11.88137
1986	8.22219
1987	11.13423
1988	7.69228
1989	9.34381
1990	7.06607
1991	11.7363
1992	14.42421
1993	7.23567
1994	9.91965
1995	9.803
1996	15.75128
1997	12.51498
1998	15.17304
1999	16.93496
2000	13.41968
2001	12.79547
2002	17.41739
2003	17.16977
2004	20.03235
2005	28.40186
2006	26.67125
2007	22.66651
2008	19.58952
2009	19.99824
2010	17.23211
2011	15.54404
2012	15.50181
2013	14.88796
2014	11.3097
2015	10.91858
2016	12.52708
2017	11.81532