Year	Percent
1983	74
1984	75
1985	75
1986	70
1987	72
1988	70
1989	71
1990	72
1991	81
1992	79
1993	81
1994	73
1995	72
1996	73
1997	76
1998	75
1999	74
2000	73
2001	71
2002	70
2003	69
2004	64
2005	72
2006	74
2007	72
2008	73
2009	70
2010	66
2011	72