Year	Percent
1961	25.97156
1962	26.04286
1963	26.10205
1964	26.17603
1965	26.24867
1966	26.37512
1967	26.44776
1968	26.5473
1969	26.64012
1970	26.73428
1971	26.97507
1972	27.02888
1973	27.09749
1974	27.17551
1975	27.22259
1976	27.26025
1977	27.27236
1978	27.11228
1979	26.60784
1980	26.69662
1981	26.84055
1982	26.95624
1983	27.08672
1984	27.20241
1985	27.34635
1986	27.47414
1987	27.60462
1988	27.73376
1989	27.92612
1990	27.99473
1991	28.0149
1992	28.3364
1993	28.5207
1994	28.88524
1995	29.12738
1996	29.37086
1997	29.60357
1998	29.82822
1999	30.07035
2000	30.30173
2001	30.34074
2002	30.42279
2003	30.81693
2004	30.80079
2005	30.61919
2006	31.00391
2007	30.91782
2008	31.05638
2009	31.72763
2010	31.52585
2011	31.79489
2012	32.06392
2013	31.93075
2014	31.93209
2015	31.93344
2016	31.93344
2017	32.06796
2018	32.06796
2019	32.06796
2020	32.06796
2021	32.06796