Year	Percent
1990	70.85
1991	70.16
1992	69.47
1993	68.79
1994	68.1
1995	67.41
1996	66.72
1997	66.04
1998	65.35
1999	64.66
2000	63.98
2001	63.6
2002	63.23
2003	62.85
2004	62.48
2005	62.1
2006	61.88
2007	61.66
2008	61.44
2009	61.22
2010	61
2011	60.78
2012	60.56
2013	60.34
2014	60.12
2015	59.9