Year	Percent
1960	19.05452
1961	19.15635
1962	18.16816
1963	17.08367
1964	16.50747
1965	16.07628
1966	16.15679
1967	16.83248
1968	16.70975
1969	16.00105
1970	16.71562
1971	15.96056
1972	15.02059
1973	14.87421
1974	14.61005
1975	14.83789
1976	13.96898
1977	27.94338
1978	11.65865
1979	9.77495
1991	7.8624
1992	7.81805
1993	8.29164
1994	8.41559
1995	8.03822
1996	8.50405
1997	8.04816
1998	8.37834
1999	8.2645
2000	8.06937
2001	7.89363
2002	7.52396
2003	7.31292
2004	6.93443
2005	6.85426
2006	6.60348
2007	6.70581
2008	7.16094
2009	7.40391
2010	6.828
2011	7.10011
2012	6.72523
2013	6.66831
2014	6.80425
2015	7.04564
2016	6.93503
2017	6.77976
2018	6.88584
2019	6.85303
2020	7.69544
2021	7.21846
2022	7.83333