Year	Percent
1990	79.23
1991	78.85
1992	78.46
1993	78.08
1994	77.69
1995	77.31
1996	76.92
1997	76.54
1998	76.15
1999	75.77
2000	75.38
2001	75
2002	74.62
2003	74.23
2004	73.85
2005	73.46
2006	73.08
2007	72.69
2008	72.31
2009	71.92
2010	71.54
2011	71.15
2012	70.77
2013	70.38
2014	70
2015	69.62