Year	Percent
1970	54.83193
1971	55.55556
1972	55.93561
1973	56.49606
1974	57.03276
1975	57.73585
1976	58.41035
1977	58.95118
1978	59.57447
1979	60.06944
1980	60.71429
1981	61.33333
1982	62.0915
1983	62.82051
1984	63.52201
1985	64.35185
1986	65
1987	65.92262
1988	66.56934
1989	67.43185
1990	68.16901
1991	69.11357
1992	69.93197
1993	70.8166
1994	71.71053
1995	72.66839
1996	73.59694
1997	74.40402
1998	75.27812
1999	76.24848
2000	76.97842
2001	77.77778
2002	78.46333
2003	79.12844
2004	79.86425
2005	80.60201
2006	81.20879
2007	81.8872
2008	82.45989
2009	83.01688
2010	83.66285
2011	84.18891
2012	84.70111
2013	85.2
2014	85.7848
2015	86.25731