Year	Percent
1961	53.30361
1962	53.70896
1963	54.11431
1964	54.51966
1965	54.92501
1966	55.33036
1967	55.73571
1968	56.05999
1969	56.62748
1970	56.91123
1971	58.69477
1972	61.12687
1973	61.00527
1974	64.20754
1975	65.34252
1976	66.43697
1977	67.49088
1978	68.09891
1979	68.788
1980	69.51763
1981	71.34171
1982	71.94974
1983	72.55776
1984	73.28739
1985	73.73328
1986	74.17916
1987	74.66559
1988	75.11147
1989	75.15201
1990	76.12485
1991	76.00324
1992	74.38184
1993	71.13904
1994	62.82935
1995	62.82935
1996	64.89664
1997	66.92339
1998	67.73409
1999	69.5987
2000	74.01702
2001	76.89501
2002	76.5302
2003	76.44913
2004	76.32752
2005	76.24645
2006	76.36806
2007	76.12485
2008	76.20592
2009	77.25983
2010	77.90839
2011	78.75963
2012	79.40819
2013	80.25942
2014	81.31334
2015	81.35387
2016	81.2728
2017	81.2728
2018	79.00284
2019	77.17876
2020	79.39197
2021	81.25091