Year	Percent
1961	19.33086
1962	19.34622
1963	19.36158
1964	19.37694
1965	19.3923
1966	19.40766
1967	19.48447
1968	19.56128
1969	19.60736
1970	19.71489
1971	19.73025
1972	19.80706
1973	19.91459
1974	19.9914
1975	20.00676
1976	20.65194
1977	20.92845
1978	21.00218
1979	21.04519
1980	21.06977
1981	21.12507
1982	21.14965
1983	21.20495
1984	21.22953
1985	20.73796
1986	20.66116
1987	20.61507
1988	20.61507
1989	20.63043
1990	20.66423
1991	20.74104
1992	21.58284
1993	21.77333
1994	21.93616
1995	21.74875
1996	23.60134
1997	24.09905
1998	24.7473
1999	25.84718
2000	28.22607
2001	30.48314
2002	30.44598
2003	30.75757
2004	31.59158
2005	32.13846
2006	32.21919
2007	32.19434
2008	32.73997
2009	32.90681
2010	34.34506
2011	34.37328
2012	34.43311
2013	34.67267
2014	34.69913
2015	38.76343
2016	38.84079
2017	38.82796
2018	38.73445
2019	39.5241
2020	39.43477
2021	39.43477