Year	Percent
1972	45.67974
1973	52.25913
1974	64.83107
1975	68.66826
1976	63.60895
1977	59.35556
1978	61.18879
1979	62.50699
1980	63.39826
1981	64.09396
1982	64.44368
1983	64.47252
1984	63.72286
1985	63.48999
1986	64.66061
1987	69.4651
1988	73.27923
1989	73.63668
1990	77.4764
1991	78.80463
1992	81.1539
1993	80.41726
1994	82.28772
1995	84.52272
1996	80.29688
1997	79.51069
1998	78.88502
1999	75.03784
2000	73.80923
2001	75.09528
2002	76.6038
2003	77.70729
2004	80.45045
2005	75.41807
2006	94.84063
2007	86.87438
2008	82.68994
2009	82.61639
2010	83.31311
2011	81.31929
2012	81.2575
2013	83.35628
2014	84.01671
2015	85.0895
2016	86.83261