Year	Percent
1961	58.8432
1962	59.35779
1963	59.24747
1964	59.43515
1965	59.59155
1966	59.71028
1967	59.80344
1968	59.99078
1969	59.7984
1970	59.88585
1971	59.80681
1972	59.85019
1973	60.12095
1974	60.29954
1975	60.43812
1976	60.42298
1977	60.40347
1978	60.74015
1979	60.73611
1980	60.63252
1981	60.67591
1982	60.80035
1983	60.69642
1984	61.0294
1985	60.99173
1986	60.94195
1987	61.06001
1988	60.90798
1989	61.04588
1990	61.01628
1991	61.07447
1992	60.97996
1993	61.00586
1994	60.97525
1995	60.85888
1996	60.73914
1997	60.87098
1998	60.835
1999	60.88444
2000	60.86897
2001	60.70483
2002	60.72938
2003	60.62478
2004	60.66716
2005	60.58341
2006	60.50942
2007	60.41323
2008	60.4593
2009	60.56391
2010	60.39742
2011	60.43004
2012	60.42063
2013	60.43946
2014	60.44955
2015	60.43172
2016	60.3991
2017	60.28394
2018	60.24356
2019	60.21981
2020	60.04586
2021	60.04593