Year	Percent
1970	75.29762
1971	75.5814
1972	76.13636
1973	76.38889
1974	76.90217
1975	77.39362
1976	78.125
1977	78.3715
1978	78.80299
1979	79.26829
1980	79.90431
1981	80.32787
1982	80.73394
1983	81.34831
1984	81.71806
1985	82.28942
1986	82.83898
1987	83.16008
1988	83.70672
1989	84.2
1990	84.67583
1991	85.16378
1992	85.60606
1993	86.05948
1994	86.65448
1995	87.07361
1996	87.65432
1997	88.04159
1998	88.58603
1999	88.96321
2000	89.49097
2001	90
2002	90.49128
2003	90.96573
2004	91.2844
2005	91.74174
2006	92.18289
2007	92.6087
2008	93.16239
2009	93.56643
2010	93.94773
2011	94.32432
2012	94.82072
2013	95.16971
2014	95.63543
2015	95.9596