Year	Percent
1961	33.94145
1962	35.00212
1963	35.53246
1964	36.06279
1965	38.21595
1966	38.74629
1967	38.23717
1968	39.31905
1969	39.84938
1970	39.31905
1971	40.91006
1972	41.44039
1973	41.97073
1974	42.00255
1975	41.47221
1976	41.49342
1977	41.52524
1978	42.0874
1979	42.10861
1980	40.62367
1981	41.68434
1982	42.74501
1983	41.79041
1984	42.32075
1985	42.47985
1986	43.54052
1987	43.59355
1988	43.64658
1989	44.17692
1990	44.73908
1991	45.82096
1992	45.29062
1993	45.29062
1994	43.16928
1995	45.39669
1996	46.45736
1997	46.9877
1998	48.5787
1999	49.63937
2000	50.16971
2001	51.23038
2002	51.23038
2003	52.82138
2004	52.82138
2005	54.94272
2006	56.05643
2007	56.05643
2008	57.64743
2009	58.17777
2010	58.17777
2011	58.17777
2012	58.17777
2013	58.81417
2014	59.93848
2015	60.52185
2016	61.11583
2017	61.69919
2018	62.29317
2019	62.87654
2020	63.47051
2021	64.17056