Year	Percent
1970	72.78481
1971	73.33333
1972	73.86018
1973	74.36662
1974	75
1975	75.46628
1976	75.94937
1977	76.51934
1978	77.20488
1979	77.73333
1980	78.27225
1981	78.89318
1982	79.62025
1983	80.19925
1984	80.78335
1985	81.3253
1986	81.96916
1987	82.71028
1988	83.31415
1989	83.90023
1990	84.46927
1991	85.13216
1992	85.76087
1993	86.48069
1994	87.07627
1995	87.76151
1996	88.22314
1997	88.77551
1998	89.31452
1999	89.84064
2000	90.35433
2001	90.85603
2002	91.25
2003	91.73004
2004	92.19925
2005	92.57196
2006	93.02112
2007	93.37568
2008	93.8061
2009	94.14374
2010	94.55663
2011	94.87847
2012	95.27491
2013	95.58199
2014	95.96299
2015	96.25624