Year	Percent
1961	9.08007
1962	9.14377
1963	9.21403
1964	9.27673
1965	9.32893
1966	9.3877
1967	9.43366
1968	9.47536
1969	9.07942
1970	8.94383
1971	8.87652
1972	8.58104
1973	8.4773
1974	8.55379
1975	8.58137
1976	8.57513
1977	8.52819
1978	8.48715
1979	8.42936
1980	8.32595
1981	8.26258
1982	8.16737
1983	8.04491
1984	7.96382
1985	7.90702
1986	7.85778
1987	7.90571
1988	7.79146
1989	7.83282
1990	7.85646
1991	7.96087
1992	7.90078
1993	7.82593
1994	7.91851
1995	7.36728
1996	7.28192
1997	7.05867
1998	7.19656
1999	7.22742
2000	7.28192
2001	7.29505
2002	7.34102
2003	7.37385
2004	7.39683
2005	7.46512
2006	7.56568
2007	7.54678
2008	7.55643
2009	7.55676
2010	7.54163
2011	7.52443
2012	7.5195
2013	7.43197
2014	7.46027
2015	7.4805
2016	7.48577
2017	7.46907
2018	7.47565
2019	7.48199
2020	7.46858
2021	7.46181