Year	Percent
1990	70.74
1991	70.6
1992	70.46
1993	70.32
1994	70.19
1995	70.05
1996	69.91
1997	69.77
1998	69.64
1999	69.5
2000	69.36
2001	69.23
2002	69.09
2003	68.95
2004	68.81
2005	68.68
2006	68.54
2007	68.4
2008	68.26
2009	68.13
2010	67.99
2011	67.85
2012	67.71
2013	67.58
2014	67.44
2015	67.3