Year	Percent
1960	84.91139
1961	85.12954
1962	84.16093
1963	83.63931
1964	83.84509
1965	83.81097
1966	85.22279
1967	85.21167
1968	85.47682
1969	86.07723
1970	85.82569
1971	85.69968
1972	85.7856
1973	85.13075
1974	84.43186
1975	85.15974
1976	86.85839
1977	88.73148
1978	90.38622
1979	88.54981
1980	88.81097
1981	88.90938
1982	89.35105
1983	89.59056
1984	90.2546
1985	90.90065
1986	92.54038
1987	95.74705
1988	97.99627
1989	99.32097
1990	100
1991	100
1992	100
1993	100
1994	100
1995	99.74011
1996	96.99029
1997	97.95309
1998	98.93235
1999	99.59228
2000	99.9798
2001	100
2002	100
2003	100
2004	100
2005	100
2006	100
2007	99.74115
2008	99.74881
2009	100
2010	100
2011	99.91819
2012	99.38881
2013	99.57753
2014	99.51674
2015	99.37461
2016	99.53988
2017	99.6372