Year	Percent
1961	5.23529
1962	5.16399
1963	5.12834
1964	5.05704
1965	5.02139
1966	4.95009
1967	4.91444
1968	4.84314
1969	4.80749
1970	4.73619
1971	4.70053
1972	4.62923
1973	4.59358
1974	4.52228
1975	4.48663
1976	4.41533
1977	4.37968
1978	4.30838
1979	4.27273
1980	4.20143
1981	4.16578
1982	4.09447
1983	4.05882
1984	3.84492
1985	3.84492
1986	3.84492
1987	3.84492
1988	3.84492
1989	3.84492
1990	3.70232
1991	3.70232
1992	3.73797
1993	3.66667
1994	3.66667
1995	3.66667
1996	3.70232
1997	3.73797
1998	3.66667
1999	3.66667
2000	3.66667
2001	3.66667
2002	3.66667
2003	3.66667
2004	3.66667
2005	3.6713
2006	3.67594
2007	3.68057
2008	3.6852
2009	3.68984
2010	3.69447
2011	3.69911
2012	3.70374
2013	3.70838
2014	3.71301
2015	3.71765
2016	3.72228
2017	3.72692
2018	3.73155
2019	3.73619
2020	3.74046
2021	3.74046