Year	Percent
1961	85.34884
1962	85.93023
1963	85.69767
1964	85.87209
1965	86.27907
1966	86.80233
1967	87.03488
1968	87.09302
1969	86.86047
1970	86.86047
1971	86.86047
1972	87.96512
1973	87.96512
1974	86.16279
1975	76.33721
1976	79.7093
1977	80.98837
1978	80.98837
1979	77.90698
1980	75.05814
1981	74.65116
1982	74.76744
1983	74.88372
1984	73.77907
1985	74.65116
1986	77.26744
1987	75.98837
1988	74.7093
1989	73.48837
1990	71.97674
1991	71.33721
1992	71.10465
1993	71.04651
1994	71.04651
1995	71.04651
1996	71.04651
1997	71.10465
1998	71.10465
1999	71.10465
2000	71.10465
2001	71.16279
2002	71.16279
2003	71.16279
2004	71.16279
2005	71.16279
2006	71.10465
2007	71.10465
2008	71.10465
2009	71.16279
2010	70.99089
2011	70.98837
2012	70.93023
2013	70.85735
2014	70.69767
2015	70.46512
2016	70.23256
2017	70
2018	69.82558
2019	69.59302
2020	69.47674
2021	69.47674