Year	Percent
1961	17.01344
1962	17.01344
1963	17.04956
1964	17.04956
1965	17.08568
1966	17.08568
1967	17.1218
1968	17.10374
1969	17.32047
1970	17.53721
1971	17.75394
1972	17.97067
1973	18.1874
1974	18.66782
1975	19.45167
1976	20.06574
1977	21.07716
1978	21.69123
1979	22.35949
1980	23.3998
1981	24.41482
1982	25.14088
1983	25.62852
1984	26.20647
1985	26.80249
1986	27.38044
1987	27.88976
1988	27.90782
1989	28.00535
1990	28.34128
1991	28.58691
1992	28.72779
1993	28.80725
1994	29.36353
1995	29.28768
1996	28.8506
1997	28.9409
1998	32.32002
1999	32.51329
2000	32.47705
2001	31.34563
2002	30.15784
2003	29.1915
2004	30.30681
2005	30.1981
2006	29.97262
2007	29.84378
2008	29.97665
2009	30.33661
2010	30.18884
2011	29.57843
2012	30.22588
2013	30.25044
2014	22.04461
2015	23.30891
2016	22.2097
2017	22.50765
2018	21.9359
2019	21.46078
2020	21.82316
2021	22.02448