Year	Percent
1961	21.30748
1962	21.30748
1963	21.27988
1964	21.27988
1965	21.25228
1966	21.22468
1967	21.22468
1968	21.22468
1969	21.19708
1970	21.19708
1971	21.16948
1972	21.16948
1973	21.14188
1974	21.14188
1975	21.11759
1976	21.00167
1977	21.00167
1978	21.00167
1979	20.97628
1980	20.97628
1981	20.94868
1982	20.94868
1983	20.92108
1984	20.45298
1985	21.9031
1986	22.79349
1987	24.00404
1988	24.36395
1989	24.52845
1990	24.88615
1991	22.92155
1992	22.82606
1993	23.19314
1994	23.1683
1995	23.72417
1996	23.71865
1997	24.02723
1998	24.22043
1999	25.32444
2000	25.12731
2001	25.92517
2002	26.60426
2003	27.23008
2004	27.64286
2005	27.76536
2006	28.36722
2007	28.91582
2008	29.09158
2009	29.48039
2010	29.49637
2011	30.04497
2012	30.06095
2013	30.34323
2014	30.519
2015	30.78531
2016	31.79728
2017	33.71471
2018	34.03428
2019	34.1408
2020	34.24732
2021	34.13374