Year	Percent
1984	69.78
1986	68.75
1987	65.44
1988	66.5
1989	65.92
1990	66.98
1991	66.92
1992	65.88
1993	66.73
1994	67.76
1995	68.56
1998	71.37
1999	70.95
2000	71.26
2001	72.21
2002	73.55
2003	74.16
2004	73.49
2005	73.52
2006	67.98
2007	67.65
2008	67.87
2009	68.09
2010	67.02
2011	69.43
2012	70.26
2013	69.13
2014	69.85
2015	70.71
2016	71.72
2017	71.51