Year	Percent
1970	83.10345
1971	83.59729
1972	84.07572
1973	84.44688
1974	84.89752
1975	85.44102
1976	85.87866
1977	86.28866
1978	86.70051
1979	87.18719
1980	87.57396
1981	88.03502
1982	88.39885
1983	88.83633
1984	89.1791
1985	89.59484
1986	90.09091
1987	90.48474
1988	90.86879
1989	91.24343
1990	91.609
1991	91.96581
1992	92.31419
1993	92.73183
1994	92.98101
1995	93.38235
1996	93.69442
1997	94
1998	94.37401
1999	94.66667
2000	95.0272
2001	95.30769
2002	95.57927
2003	95.92145
2004	96.18263
2005	96.43917
2006	96.76233
2007	97.00948
2008	97.25036
2009	97.48924
2010	97.72242
2011	97.95198
2012	98.178
2013	98.40056
2014	98.61878
2015	98.83482