Year	Percent
1961	72.82784
1962	72.80479
1963	72.82784
1964	73.13513
1965	74.03396
1966	74.13382
1967	74.47953
1968	74.27979
1969	74.32588
1970	74.49489
1971	74.47953
1972	76.75348
1973	76.73811
1974	76.73811
1975	76.85335
1976	76.80725
1977	76.75348
1978	76.72275
1979	76.69202
1980	76.72275
1981	76.67665
1982	76.65361
1983	76.54606
1984	77.28355
1985	77.03004
1986	77.13759
1987	77.70608
1988	80.10294
1989	80.22586
1990	79.78797
1991	79.28094
1992	73.35792
1993	72.56664
1994	71.8906
1995	72.01352
1996	71.65245
1997	71.94438
1998	72.47446
1999	72.87393
2000	72.21326
2001	72.23631
2002	71.85219
2003	71.66014
2004	71.62173
2005	71.52954
2006	71.29139
2007	71.18384
2008	71.08397
2009	71.03019
2010	70.99178
2011	70.12368
2012	70.08527
2013	71.27602
2014	71.59868
2015	72.4763
2016	73.1137
2017	73.45264
2018	73.95944
2019	75.83929
2020	76.26949
2021	77.34501