Year	Percent
1961	22.80922
1962	23.44927
1963	24.38881
1964	24.83901
1965	25.32835
1966	25.85684
1967	26.34618
1968	26.81595
1969	27.24657
1970	27.88859
1971	28.18415
1972	29.81072
1973	31.47449
1974	33.04625
1975	33.70589
1976	34.3479
1977	35.16413
1978	35.9686
1979	36.60671
1980	37.06864
1981	37.85746
1982	38.71479
1983	38.94772
1984	39.2472
1985	40.27677
1986	40.66433
1987	41.57451
1988	41.75067
1989	41.76437
1990	41.85441
1991	42.11474
1992	41.83679
1993	41.58429
1994	41.76633
1995	41.94836
1996	42.1304
1997	42.31244
1998	42.49251
1999	42.67455
2000	42.85658
2001	43.03862
2002	43.22065
2003	43.40269
2004	43.58472
2005	43.76676
2006	43.9488
2007	44.12887
2008	44.31091
2009	44.49294
2010	44.67498
2011	44.68281
2012	44.69064
2013	44.69899
2014	44.71021
2015	44.71804
2016	44.71021
2017	44.72
2018	44.71745
2019	45.01948
2020	45.55168
2021	45.99816