Year	Percent
1970	66.48045
1971	66.9708
1972	67.44186
1973	68.07018
1974	68.50258
1975	68.97133
1976	69.42149
1977	70.12987
1978	70.5414
1979	71.09375
1980	71.62577
1981	72.13855
1982	72.67356
1983	73.14949
1984	73.64672
1985	74.22969
1986	74.69051
1987	75.37212
1988	75.79787
1989	76.33987
1990	76.96268
1991	77.46835
1992	77.95766
1993	78.43137
1994	78.98551
1995	79.54816
1996	80.07034
1997	80.48499
1998	81.09339
1999	81.59371
2000	82.17054
2001	82.64192
2002	83.10011
2003	83.6518
2004	84.08377
2005	84.69493
2006	85.11723
2007	85.61368
2008	86.09732
2009	86.56863
2010	87.02807
2011	87.48806
2012	87.92453
2013	88.36127
2014	88.77645
2015	89.19164