Year	Percent
1970	85.08671
1971	85.55176
1972	86.00224
1973	86.43881
1974	86.86211
1975	87.27273
1976	87.67123
1977	88.16199
1978	88.53634
1979	89.00101
1980	89.45274
1981	89.79392
1982	90.31008
1983	90.72658
1984	91.13208
1985	91.43389
1986	91.81985
1987	92.19601
1988	92.56272
1989	92.92035
1990	93.35083
1991	93.60415
1992	93.93681
1993	94.34122
1994	94.57429
1995	94.96284
1996	95.26144
1997	95.55735
1998	95.84333
1999	96.12342
2000	96.39781
2001	96.66667
2002	96.93016
2003	97.26236
2004	97.43976
2005	97.76119
2006	97.93052
2007	98.1685
2008	98.40232
2009	98.63211
2010	98.78658
2011	98.93843
2012	99.22753
2013	99.30362
2014	99.51624
2015	99.72565