Year	Percent
1990	71.03
1991	70.8
1992	70.58
1993	70.35
1994	70.13
1995	69.91
1996	69.68
1997	69.46
1998	69.23
1999	69.01
2000	68.78
2001	68.56
2002	68.34
2003	68.11
2004	67.89
2005	67.66
2006	67.44
2007	67.22
2008	66.99
2009	66.77
2010	66.54
2011	66.32
2012	66.1
2013	65.87
2014	65.65
2015	65.42