Year	Percent
1961	11.90573
1962	11.88497
1963	11.88497
1964	11.85382
1965	11.85382
1966	11.82267
1967	11.82267
1968	11.80191
1969	11.80191
1970	11.78115
1971	11.78115
1972	11.78115
1973	11.78115
1974	11.78115
1975	11.78115
1976	11.78115
1977	11.83306
1978	11.83306
1979	11.83306
1980	11.83306
1981	11.83306
1982	11.87458
1983	11.9265
1984	11.93688
1985	11.95764
1986	12.05108
1987	12.11337
1988	12.08223
1989	12.08223
1990	11.04402
1991	11.35818
1992	11.66861
1993	11.98078
1994	12.29307
1995	12.60914
1996	12.92797
1997	13.24207
1998	13.56667
1999	13.87811
2000	14.19348
2001	14.50678
2002	14.82114
2003	15.13546
2004	15.44958
2005	15.75958
2006	16.06936
2007	16.37439
2008	16.68627
2009	16.99679
2010	17.30725
2011	17.61482
2012	17.92604
2013	18.23662
2014	18.54623
2015	18.85853
2016	19.17029
2017	19.48389
2018	19.79759
2019	19.96512
2020	19.96512
2021	19.96512