Year	Percent
1961	27.73193
1962	27.63962
1963	27.515
1964	27.58054
1965	27.6147
1966	27.64793
1967	27.68208
1968	27.71531
1969	27.93409
1970	27.96732
1971	28.37072
1972	28.8655
1973	28.90058
1974	29.39444
1975	29.89015
1976	29.92338
1977	30.41909
1978	30.45232
1979	30.94711
1980	30.98126
1981	31.47697
1982	31.51112
1983	31.54528
1984	32.04745
1985	32.01975
1986	32.49608
1987	32.51823
1988	32.53946
1989	32.74255
1990	32.7287
1991	33.04348
1992	33.07579
1993	33.42841
1994	33.5558
1995	33.78565
1996	33.8632
1997	34.03859
1998	34.13828
1999	34.21859
2000	34.2869
2001	34.2989
2002	34.44198
2003	33.82904
2004	33.80135
2005	34.11982
2006	34.24582
2007	34.33583
2008	34.41475
2009	34.49368
2010	34.5726
2011	34.65707
2012	34.74615
2013	34.83615
2014	34.84616
2015	34.84707
2016	34.87975
2017	34.77481
2018	34.96409
2019	35.07378
2020	35.08509
2021	35.18819