Year	Percent
1961	93.44075
1962	92.84082
1963	92.22375
1964	91.89807
1965	91.26386
1966	90.93246
1967	90.51537
1968	89.82973
1969	89.40692
1970	88.45275
1971	88.2242
1972	87.98994
1973	87.7614
1974	87.53857
1975	87.31002
1976	87.07576
1977	86.85293
1978	86.62439
1979	86.39584
1980	86.1673
1981	86.00731
1982	85.82448
1983	85.65878
1984	85.48737
1985	85.32168
1986	85.10456
1987	84.89316
1988	84.7846
1989	84.68746
1990	85.23026
1991	85.25311
1992	85.27597
1993	85.30454
1994	85.32739
1995	85.35025
1996	85.36739
1997	85.39024
1998	85.41881
1999	85.44166
2000	85.46452
2001	85.48737
2002	85.26454
2003	85.2874
2004	84.72746
2005	84.7446
2006	83.96183
2007	83.13336
2008	83.84185
2009	84.64176
2010	82.46486
2011	82.99623
2012	81.34499
2013	81.97177
2014	82.70541
2015	82.66255
2016	81.50668
2017	81.26443
2018	81.08102
2019	80.7182
2020	80.3531
2021	80.38856