Year	Percent
1990	67.8
1991	67.56
1992	67.33
1993	67.1
1994	66.87
1995	66.63
1996	66.4
1997	66.17
1998	65.93
1999	65.7
2000	65.47
2001	65.24
2002	65.01
2003	64.78
2004	64.55
2005	64.33
2006	64.1
2007	63.88
2008	63.66
2009	63.43
2010	63.21
2011	62.99
2012	62.77
2013	62.55
2014	62.33
2015	62.11