Year	Percent
1960	99.19133
1961	99.24495
1962	99.49817
1963	99.68457
1964	99.61409
1965	99.51815
1966	99.21774
1967	99.04561
1968	99.24781
1969	99.60969
1970	99.89347
1971	99.90889
1972	99.91284
1973	99.84656
1974	99.8477
1975	99.87395
1976	99.80761
1977	99.55769
1978	99.48288
1979	99.54332
1980	99.907
1981	97.13965
1982	95.12984
1983	96.24029
1984	96.7693
1985	98.88807
1986	100
1987	100
1988	100
1989	100
1990	98.87832
1991	98.77155
1992	98.72272
1993	99.21886
1994	99.0144
1995	98.7026
1996	97.1512
1997	96.1301
1998	95.01496
1999	96.45691
2000	97.17154
2001	97.11859
2002	98.92858
2003	100
2004	100
2005	100
2006	100
2007	100
2008	100
2009	99.5578
2010	99.95115
2011	99.85202
2012	99.21921
2013	99.29017
2014	99.60908
2015	100
2016	100
2017	100