Year	Percent
1961	66.34889
1962	66.15299
1963	65.89833
1964	65.72203
1965	65.12129
1966	65.12456
1967	64.70665
1968	64.56953
1969	63.85125
1970	63.80554
1971	63.69127
1972	63.24398
1973	63.09706
1974	62.87179
1975	62.76405
1976	62.68243
1977	62.55183
1978	62.39512
1979	62.18943
1980	62.05557
1981	61.73887
1982	61.67684
1983	61.63766
1984	61.83356
1985	61.75193
1986	61.63766
1987	61.60501
1988	61.44504
1989	61.40259
1990	61.35688
1991	61.22629
1992	61.19364
1993	61.10222
1994	61.0761
1995	60.79859
1996	60.31539
1997	60.25988
1998	60.21418
1999	60.18806
2000	60.11623
2001	58.07568
2002	55.1732
2003	52.79846
2004	53.29873
2005	51.9244
2006	52.09258
2007	50.49948
2008	50.93373
2009	50.99582
2010	47.17579
2011	48.26111
2012	47.44628
2013	47.05921
2014	47.108
2015	46.93491
2016	46.94471
2017	47.23211
2018	47.3985
2019	47.44373
2020	48.12661
2021	47.36838