Year	Percent
1961	70.32403
1962	70.21863
1963	69.73581
1964	69.57261
1965	69.49781
1966	69.3788
1967	69.2904
1968	69.2088
1969	68.77359
1970	68.61378
1971	60.00816
1972	59.52875
1973	59.44035
1974	59.50835
1975	59.55935
1976	59.60015
1977	59.50495
1978	59.80415
1979	59.86876
1980	59.71235
1981	59.67495
1982	59.62395
1983	58.68553
1984	58.63112
1985	58.12451
1986	57.94431
1987	57.8423
1988	57.25409
1989	57.29149
1990	57.25749
1991	54.58502
1992	54.32661
1993	54.09541
1994	53.38819
1995	52.13356
1996	52.18796
1997	52.17436
1998	52.64697
1999	53.718
2000	52.87808
2001	52.42156
2002	51.64718
2003	50.40951
2004	50.32835
2005	49.83126
2006	48.02887
2007	47.89022
2008	48.88847
2009	47.28288
2010	48.45089
2011	46.84395
2012	46.42599
2013	46.09121
2014	44.50862
2015	43.77481
2016	43.32506
2017	43.37433
2018	41.94875
2019	44.37
2020	42.33226
2021	41.94223