Year	Percent
1961	12.42474
1962	12.42474
1963	12.47947
1964	12.47947
1965	12.2058
1966	12.2058
1967	12.09633
1968	11.98686
1969	12.09633
1970	12.09633
1971	12.09633
1972	12.58894
1973	12.86262
1974	13.13629
1975	13.40996
1976	14.23098
1977	14.77833
1978	15.32567
1979	15.59934
1980	15.87302
1981	16.42036
1982	16.96771
1983	17.51505
1984	18.0624
1985	18.88342
1986	19.15709
1987	19.97811
1988	20.79912
1989	21.62014
1990	22.44116
1991	23.20744
1992	22.88998
1993	22.57252
1994	22.25506
1995	21.9376
1996	21.62014
1997	21.30268
1998	20.98522
1999	20.66776
2000	20.3503
2001	20.03284
2002	19.71538
2003	19.39792
2004	19.08046
2005	18.763
2006	18.44554
2007	18.12808
2008	17.81062
2009	17.50411
2010	17.46579
2011	17.42748
2012	17.38916
2013	17.35085
2014	17.31253
2015	17.27422
2016	17.23591
2017	17.19759
2018	17.15928
2019	17.12096
2020	17.05528
2021	17.05528