Year	Percent
1961	28.39602
1962	28.61574
1963	28.83547
1964	29.05519
1965	29.22321
1966	29.49464
1967	29.71436
1968	29.93408
1969	30.15381
1970	30.37353
1971	30.59325
1972	30.76128
1973	30.85175
1974	31.07147
1975	31.16195
1976	31.25242
1977	31.31705
1978	31.4463
1979	31.57555
1980	31.73064
1981	31.92452
1982	32.14424
1983	32.33812
1984	32.48029
1985	32.67416
1986	32.86804
1987	33.06191
1988	33.29456
1989	33.48843
1990	33.63061
1991	34.07005
1992	34.5095
1993	34.94895
1994	35.46594
1995	35.82784
1996	36.79721
1997	37.27284
1998	37.53393
1999	38.36112
2000	38.92982
2001	39.39511
2002	39.98966
2003	40.45496
2004	41.3597
2005	41.6182
2006	42.13519
2007	41.8767
2008	42.52294
2009	42.13519
2010	41.8767
2011	42.39369
2012	41.8767
2013	41.8767
2014	41.8767
2015	41.8767
2016	41.8767
2017	41.8767
2018	41.8767
2019	41.8767
2020	41.8767
2021	41.8767