Year	Percent
1970	59.55414
1971	60.24845
1972	60.60606
1973	61.06195
1974	61.49425
1975	62.07865
1976	62.73973
1977	63.2
1978	63.80208
1979	64.46701
1980	64.85149
1981	65.3012
1982	66.11765
1983	66.74312
1984	67.33781
1985	67.97386
1986	68.57749
1987	69.35818
1988	69.95968
1989	70.72692
1990	71.31931
1991	72.25326
1992	73.13975
1993	73.85159
1994	74.74227
1995	75.75251
1996	76.50897
1997	77.2293
1998	77.91602
1999	78.7234
2000	79.46429
2001	80.05822
2002	80.62678
2003	81.31102
2004	81.94254
2005	82.57373
2006	83.04862
2007	83.74194
2008	84.3038
2009	84.84472
2010	85.34799
2011	85.85132
2012	86.43868
2013	86.90614
2014	87.47153
2015	88.00448