Year	Percent
1961	55.49509
1962	55.54664
1963	55.57242
1964	55.73282
1965	55.95051
1966	55.94191
1967	55.60107
1968	55.2373
1969	55.14851
1970	54.48687
1971	54.2835
1972	54.27491
1973	54.12597
1974	53.90829
1975	53.82522
1976	53.72784
1977	53.58749
1978	53.44428
1979	53.2581
1980	53.04328
1981	52.87715
1982	52.69097
1983	52.50193
1984	52.37018
1985	52.25561
1986	52.15249
1987	51.91476
1988	51.83456
1989	51.71713
1990	51.64838
1991	49.082
1992	48.55212
1993	49.15788
1994	49.5775
1995	49.67918
1996	49.66341
1997	49.64045
1998	49.77652
1999	49.14895
2000	48.91245
2001	48.82201
2002	48.63556
2003	48.74
2004	48.78
2005	48.83301
2006	48.59486
2007	48.6133
2008	48.5357
2009	48.43808
2010	47.91003
2011	47.96592
2012	47.81087
2013	47.85886
2014	47.93637
2015	47.95907
2016	47.68434
2017	47.76312
2018	47.64154
2019	47.70028
2020	47.49707
2021	47.48562