Year	Percent
1970	87.471
1971	87.89954
1972	88.21549
1973	88.72928
1974	89.13043
1975	89.50749
1976	89.88409
1977	90.34268
1978	90.6953
1979	91.03726
1980	91.45978
1981	91.87867
1982	92.18901
1983	92.5785
1984	92.96435
1985	93.24699
1986	93.60731
1987	93.96396
1988	94.30605
1989	94.55663
1990	94.88291
1991	95.20137
1992	95.51228
1993	95.8159
1994	96.11249
1995	96.32052
1996	96.68016
1997	97.03288
1998	97.22222
1999	97.56289
2000	97.81931
2001	98.07099
2002	98.31804
2003	98.56061
2004	98.7988
2005	99.10648
2006	99.26199
2007	99.48793
2008	99.70972
2009	99.85612
2010	100.07138
2011	100.28329
2012	100.42164
2013	100.62762
2014	100.76125
2015	100.89286