Year	Percent
1961	49.99051
1962	50.31332
1963	50.46523
1964	50.57157
1965	50.32851
1966	50.25635
1967	50.30952
1968	50.31332
1969	49.71706
1970	49.70567
1971	49.69807
1972	51.21644
1973	51.20068
1974	51.18492
1975	52.95469
1976	54.51179
1977	54.21822
1978	55.0602
1979	54.8517
1980	55.41377
1981	57.67916
1982	55.52391
1983	55.41567
1984	54.96563
1985	54.66181
1986	54.64661
1987	54.20987
1988	53.89085
1989	53.55095
1990	52.85405
1991	52.25241
1992	51.65491
1993	51.05592
1994	50.45685
1995	49.85783
1996	49.25879
1997	48.65999
1998	48.06122
1999	47.46248
2000	46.86382
2001	46.26517
2002	45.66634
2003	45.03437
2004	45.1559
2005	44.47989
2006	43.20003
2007	43.62538
2008	43.19623
2009	43.63678
2010	43.32536
2011	43.18484
2012	42.57111
2013	42.17842
2014	42.2164
2015	40.68209
2016	40.3099
2017	40.42384
2018	39.86936
2019	39.28829
2020	38.56291
2021	38.64266